34.Hoa received (her aunt’s) letter five days ago.

->Whose letter did Hoa receive five days ago?

35. There are (twelve) students in Lien’s class having toothache.

->How many students are there in Lien's class having toothache?
 

36, My bother plays video games twice a week.

=> How often does your brother play video games?

37, We rarely eat out because it is far too expensive.

=> Why do you rarely eat out?

38, Minh usually spends one hour on computer games.

=> How long does Minh usually spend on computer games?

39, Her son is going to invent a new game.

=> What is her son going to?

40, There are thousands of books in the new public library.

=> How many books are there in the new public library?