_____did you spend on the skirt? [ ]

He is a very hard-working student．—．As far as I know, he often burns the midnight oil．

We tried our best to ______, but she didn’t stop crying.

Can you tell me _____ the birdwatchers in Zhalong Nature Reserve? I only know that _____ of them are from our school.

IfBetty has time, she______ climbing with her parents tomorrow.[ ]