Theory:

11. The cobra stood on the defensive, swaying slowly from side to side, trying to mesmerise the mongoose into making a false move. But the mongoose knew the power of his opponent’s glassy, unwinking eyes, and refused to meet them. Instead he fixed his gaze at a point just below the cobra’s hood, and opened the attack.
 
12. Moving forward quickly until he was just within the cobra’s reach, the mongoose made a pretended move to one side. Immediately the cobra struck. His great hood came down so swiftly that I thought nothing could save the mongoose. But the little fellow jumped neatly to one side, and darted in as swiftly as the cobra, biting the snake on the back and darting away again out of reach.
 
13. At the same moment that the cobra struck, the crow and the myna hurled themselves at him, only to collide heavily in mid-air. Shrieking insults at each other they returned to the cactus plant. A few drops of blood glistened on the cobra’s back.
 
14. The cobra struck and missed. Again the mongoose sprang aside, jumped in and bit. Again the birds dived at the snake, bumped into each other instead, and returned shrieking to the safety of the cactus.
 
15. The third round followed the same course as the first but with one dramatic difference. The crow and the myna, still determined to take part in the proceedings, dived at the cobra; but this time they missed each other as well as their mark. The myna flew on and reached its perch, but the crow tried to pull up in mid-air and turn back. In the second that it took the bird to do this the cobra whipped his head back and struck with great force, his snout thudding against the crow’s body.
 
16. I saw the bird flung nearly twenty feet across the garden. It fluttered about for a while, then lay still. The myna remained on the cactus plant, and when the snake and the mongoose returned to the fight, very wisely decided not to interfere again! The cobra was weakening, and the mongoose, walking fearlessly up to it, raised himself on his short legs and with a lightning snap had the big snake by the snout. The cobra writhed and lashed about in a frightening manner, and even coiled itself about the mongoose, but to no avail. The little fellow hung grimly on, until the snake had ceased to struggle. He then smelt along its quivering length, gripped it round the hood, and dragged it into the bushes.
 
17. The myna dropped cautiously to the ground, hopped about, peered into the bushes from a safe distance, and then, with a shrill cry of congratulation, flew away.
Explanation:
  
The cobra was trying to trap the mongoose with his false movements, but the mongoose was well aware of the power of its opponent. So he fixed his focus on attacking the cobra at a point just below the cobra's hood and started the attack.

The mongoose made false quick movements very close to the cobra. The cobra attacked and moved its hood down so quickly that it seemed the mongoose would not be saved. But this small creature was quick to jump and move on one side. It also bit the snake on its back and again moved away out of its reach.

The moment the cobra was attacked, the crow and myna threw themselves at him. When they flew towards the cobra, they hit each other. It must have been painful because they made loud noises at each other, and they went back to the cactus. Here, the boy perceives the noises made by the birds as insults; he feels that the birds were insulting each other for having collided. By using the phrase "shrieking insults", the boy has personified the birds.
 
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Birds collided

Drops of blood were shining on the cobra's back. And it was a strong hit by the mongoose.

The cobra was trying to attack the mongoose but missed it. The mongoose again jumped aside. The birds again tried to attack the cobra but collided with each other. So they went back safely to the cactus.

Third time again, the birds tried to attack the cobra in the same manner, but this time there was a change. They didn't collide with each other. The myna flew back to its shelter, but the crow tried to continue the fight in the air, and it swerved. In the second trial, the cobra also moved suddenly and attacked the crow with full force.

The boy noticed the crow falling twenty feet away. It kept shaking its body for some time, but then it became still and died. The myna was on the cactus, and she didn't interfere in the fight after the crow's death. The cobra was weakened and exhausted. The mongoose attacked fearlessly, when the cobra became tired of moving, the mongoose made a fast attack, showing his ability to assess the cobra's power accurately, and turned it into his victory. Finally, the cobra was killed by the mongoose. It caught the cobra just below its hood and dragged it into the bushes.
 
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The mongoose dragged the cobra into the bushes

The myna rushed to the ground and hopping about she reached near to the bushes. Then, she flew away with a congratulatory squeal.
 
 
Glossary from the paragraphs \(11\) - \(17\) of "The Banyan Tree":
 
No.
Words
Meanings
1.
DefensiveDefending, protective/ Used or intended to defend or protect
2.
PretendedActed/ Behave so as to make it appear that something is the case when in fact it is not
3.
CollideWhen anyone collides with another, it is to clash on the other person without an intention to do so
4.
GlistenedAny shining surface which reflects light
5.
PerchRepose/ Settle on something
6.
MesmeriseHere in this lesson, it is magically persuade/ To capture the complete attention of someone
7.
A false moveAny action performed to confuse and/or cheat an opponent
8.
RoundHere in this lesson, it is a stage in a fight or competition
9.
Pull upHere in this lesson, it is meant as stop/ Come to a halt
10.
Whipped...backMoved...back suddenly
11.
SnoutThe nose and mouth of an animal
12.
To no availWith no success
13.
GrimlyIn a very serious manner
14.
ShrillHigh-pitched (of a voice or sound) and piercing
15.
DivedMove suddenly or quickly in a specified direction/ Moving downwards through the air
16.
SprangMove or jump suddenly or rapidly upwards or forwards
17.
Hurled Threw someone or something with great force
18.
ShriekingExtremely shrill sound that hurts the ears
19.
SwervedChange or cause to change direction abruptly
20.
SquealA long, high-pitched cry or noise
Reference:
National Council of Educational Research and Training (2007). The Banyan Tree (pp. 124-138). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.