"Idealist youth" refers to "idealistic youth". The most difficult word in this sentence is "big gesture". This is a fixed usage, but it is not impossible to infer: grand means "big, grand and great", gesture means "gesture", and so on. Here, big gesture means "great selfless image, loving behavior". Mom made a joke, but because of the high-profile and selfless spirit of the joke, an idealistic youth was influenced, which led the children to take it seriously and really sell their big house.
There are four options for this question:
A. Don't give an unthinking answer to the ideal youth-although it makes sense, it has little to do with the original sentence.
B. Never give your child an answer right away unless he is an idealist. -Exactly the same as the above options.
C. If the child is rational, you can give him an answer. -it's a bit like saying the original intention in reverse.
D. don't seriously respond to the child's request without thinking. First of all, the meaning is similar to the first two, and "children's demands" doesn't seem to match the examples in the article.
Reluctantly, but option d is really deceptive. So I think the answer is C.
Finally, spit out one sentence. This question is not very interesting. It feels like a brain teaser. Even so, I wish you good luck in the exam. Don't be discouraged by this reading comprehension! Good luck!