题目

 My grandma is ill. I have to ________ her at home.    A. look for      B. look up              C. look at                     D. look after 答案： D   look for “寻找”；look up “（在词典等中）查找”；look at “看……”；look after “照顾”。由句意“我奶奶生病了，我不得不在家照顾她”知选D。308000000吨≈ 亿吨．