【正确答案】 A

【答案解析】从第二段John．．．tried to think what it would be like to have toothache all the time and how bad-tempered that would make you．意思是John想，要是自己牙齿总是疼又会怎样呢?那时自己的脾气还不知道会多么坏呢!由此可看出John是站在母亲的角度米体会母亲为什么会发脾气的。