Theory:

     “This is only a stone,” protested the ghost. “And anyway it is too dark to see.”
 
     “Never heard of a ghost who can’t see in the dark!” remarked Vijay Singh. “That stone which you hold in your hand contains salt. Crumble it and see.” Again the ghost tried to crush the stone, but in vain. He handed over the stone to Vijay Singh. The ghost was now beginning to doubt his ghostly powers.
 
     “I can see that you’re not going to be a worthy opponent. What’s the use of wrestling with a weakling whom I can floor in a minute?” So saying, Vijay Singh casually crumbled the lump of salt and let the stone drop in the darkness. He held out his hand and commanded the ghost to taste the powdered stone.
Explanation:
 
The ghost had not accepted but disagreed with Vijay's Singh' words. The ghost had already been cheated by Vijay Singh with the first stone when Vijay Singh claimed to have broken an eggshell. It never wanted to compromise the next time. It just gave an excuse saying that it wouldn't be able to see anything since it was too dark. Vijay Singh was amazed by the words of the ghost.

Vijay Singh made a sarcastic remark saying he never heard of a ghost who couldn't see in the dark. While Vijay Singh was ready with the lump of salt in his hands, he claimed the stone the ghost possessed to be containing salt. He challenged the ghost to break it. The ghost tried to break the stone but ended up in failure in his second attempt as well. So, it handed it over to Vijay Singh again. The ghost has started to doubt its ghostly powers. Vijay Singh confused the ghost again.

Vijay Singh started to comment on the ghost and its powers most disrespectfully. He also explained the fact that fighting against an unworthy opponent like this ghost is useless for him. Moreover, Vijay Singh also informed the ghost that it would hardly take a minute to defend a weak opponent like the ghost for him. On explaining these facts, he pretended to have crushed the stone into salt powder. Vijay Singh dropped the stone in the sand trickily. He also shared the powdered salt and ordered the ghost to taste it.
 
Meaning of difficult words:
 
S.No
Words
Meaning
1.
Protested
To disagree or disapprove something
2.
Crumble
To break something into small pieces
3.
Vain
Unsuccessful or failing to produce the expected result
4.
Worthy
Having value or importance
5.
Opponent
A person against someone
Reference:
National Council of Educational Research and Training (2006). A Strange Wrestling Match: Indira David (pp. 43-51). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.