题目

It was＿＿＿＿computer games that cost the boy a lot of time that he ought to have spent on his lessons. A.to have played B.playing C.played D.having played   答案：B本题为强调句型，被强调的部分是句子的主语，所以采用-ing形式。2．若函数f（x）的定义域为[-1，2]，则函数f（2x-1）的定义域为[0，$\frac{3}{2}$]．