To know ________ the mountain top looks like, you need to reach it.
what
when
where
which
-- Mary is going to Shanghai for the winter vacation. -- _______________
The boys don’t know ___________.
The girl has been lonely since her mother ______________.
-- You used to be short, didn’t you? -- _______. I was the shortest in my class.
I think students should _______ to have at least one hour a day for sports.