Theory:

     I remembered my class teacher, an English woman, telling us in class one day, “When I crossed the English Channel on my way to Singapore, there was a big storm near Gibraltar. The ship rocked to and fro. Everything in the cabins rolled up and down. Even the heavy pianos in the lounge went crashing against the walls.
 
     This made my imagination run wild. Turning to Uncle again, I said, “Wouldn’t it be fun if the storm broke when we have lunch? Then the tables, with all the food on them, would run away from us. And the chairs, with us sitting on them, would be a merry-go-round.”
Explanation:
 
Vasantha was reminded of her teacher's narration on her journey during the class. Her English teacher once explained how there had been a big storm near Gibraltar while crossing the English Channel on her way to Singapore. The English Channel is the busiest shipping area in the world. Gibraltar is a British Overseas Territory located at the southern tip of the Iberian Peninsula. From side to side, the ship swung back and forth. The things of the cabin went up and down. It seems that even the pianos that were too large collided with the wall.

Vasantha's imagination was inspired by the enormous explanation provided by her class teacher about her travel experience.

"Wouldn't it be fun if the wind broke when we were having lunch?" she asked a person near her. She imagined how wonderful it would be to have lunch on a ship during a storm in her specific way. The tables with all the food items on them would move, and their chairs, if they were on them, would be a merry-go-round.
 
Meaning of difficult words:
 
S.No
Words
Meaning
1.
Rock
To move back and forth or sideways
2.
Lounge
A room with seating where people can wait
3.
Crash
To break violently often with a loud noise
4.
To and froBackwards and forwards
5.
Narration A spoken description of events
6.
Imagination The ability to form ideas, or pictures of people or things
7.
WildExtremely violent and not controlled by others
Reference:
State Council of Educational Research and Training (2018). Term-3 English Standard-7. Man Overboard - Vasantha Murthi (pp. 125-130). Published by the Tamil Nadu Textbook and Educational Services Corporation.