Tom and Mike were good friends. ____  , sometimes they were not. But some of their classmates said they were like brothers. One day they went out for a walk together. ____  and they went into a restaurant to have lunch. The waiter came up to them and asked, “What can I do for you?”“Please bring us two apples first.” Said Tom. When the waiter put the two apples on the table ____  Tom got angry. “ You are impolite (没礼貌). Why didn’t you take the smaller one?” Tom said.
    “But I was right,” said Mike with a smile. “If I let you take first, which one will you choose?”“Of course ____.” said Tom. “Yes,” Mike said, “If you take the smaller one, the bigger one will be mine. ____ ?”“Oh.” Tom couldn’t answer.

在点燃条件下，A和B反应生成C和D．反应前后分子变化的微观示意图如下．

回答问题：