What on earth are the police busy with?—They have been looking into how the plane crash _______.

What are your parents doing now?- Well, my father is reading a newspaper_______ my mother is cooking.

The museum _________ from 9:00 a.m. to 5:00 p.m. at the weekend. Let’s go together.

Do you know if foreign students _______school uniform?— Yes. Most British students do so.

What do you think of Ann?—Ann is so careful that she always goes over her exercises to ______ there are no mistakes.