Theory:

     As we turned, I spotted two rows of resplendent cavalry officers, mounted on their magnificent horses coming towards us. They obviously belonged to the governor's bodyguard. I could only cling on helplessly as the frightened cow charged straight at the horses. The horses panicked and scattered. There was a regular stampede. The cow managed to fall into a ditch and in the process, dislodged me, and I landed on the soft earth bordering the ditch.
Explanation:
 
The author sits on the top of the cow and as she takes a turn around the corner, she witnessed someone approaching her. She did not want to be seen in this awkward position, but had to face them. To make things more worse for her, it was not a single person that was approaching her, nor was it any normal townsfolk. She saw two rows of Cavalry officers mounted on their magnificent horses riding towards her direction. Cavalry officers are soldiers or warriors who fight for the government. They mostly fight mounted horses that are especially trained for this purpose of war.
 
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Cavalry officers
 
The author easily guessed that they belonged to the governor's bodyguard, as only highly influential people would need cavalry officers. The cow who was already confused by the sudden attack, was even more triggered by the horses' hooves and the extra noise of the cavalry officers parading the roads. He makes a straight dash towards the horses' direction, not realising the consequences it would cause. It was also frightened by the confusions. Generally one tends to make illogical decisions when one is scared. The same theory applies to animals, especially as they do not have the sixth sense to feel or think.
 
The author clings onto the cow's body not knowing a way to escape. The horses who saw the cow raging towards them, also got confused and scared and started running. They scattered to every corner, thereby pulling the riders down. The cavalry officers who were the symbol of protection and bravery, come tumbling down the horse's backs. There was a stampede, with people falling down and animals running across in every direction. The cow, who had by now had enough, loses control and falls into a ditch. In the process of falling into the ditch the cow brushes off the author into the side of the ditch. Every ditch has fresh earth near it, which is the part that is removed from the ground to make a ditch. The author is lucky to fall in the fresh earth, and escape without bruises.
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The horses panic and run in different directions with the cavalry officers
 
Words with difficult meaning:
 
S.No
Words
Meaning
1
ResplendentShiny and colorful
2
CavalryMilitary
3
MountedOn horseback 
4
MagnificentGrand
5
ObviousEasily seen 
6
PanickedFeared 
7
StampedeA situation in which many people run around and fall over each other
8
DitchA pit that is dug on the earth
9
DislodgedTo remove
10
TriggeredTo start to initiate an action
Reference:
State Council of Educational Research and Training (2019). Term-3 English Standard-6. That Sunday Morning (pp 91-105). Published by the Tamil Nadu Textbook and Educational Services Corporation.