1.My sister is ill and she couldn’t e____________ walk.
2.How many times have you been to Beijing?
T___________.
3.You shouldn’t ask her age, It’s a s______________.
4.The scientists d___________this desert in 1990 and now they have found something useful.
5.I had a good time in the park yesterday and I kept a d____________last night.
6 很难弄清楚宇宙到底有多大．
It is ______ _______ understand how _________ _______
7. 科学家认为地球上的生命已有数百万年．
Scientists think that _______ ______ ______ life on Earth for _______ _____ years.
