On rainy days, accidents ______ happen sometimes on steep roads．

—Steve is good at writing short stories. — So he is. But he writes _______ than us. So he can’t get good grades in writing. 

---Could I go boating this weekend, Dad?---Yes, you ________. But you ________ come back before lunch.

Tom’s uncle knows computers well, and he __________ a computer engineer .

(2014·济南市名校第四次诊断性测试)—Is the letter from your mother?—Yes.But she ________the letter herself，because she doesn’t even know one word.