-- Why didn’t you do your math homework last weekend? -- My cousin borrowed my math book and didn’t_____ __it.
--Do you mind if I open the window? ---______. We should let in more fresh air.
--I will go to Beijing for a visit with my family during the long holiday of May. ---______.
---Who is the tallest boy? ---It ______ be John. John is of medium height.
These young trees must ______.
I found ______ not very difficult to keep away from the A/H1N1 Flu.