None of us was good at swimming, so the crossing of this dangerous river was really a_________.

Many teens don't get enough sleep because they have too much homework to do, which ________ them up at night.

----Did you look up the time of the high-speed trains to Shanghai?----Yes, the early train is __________ to leave at 5:30 a.m.

Judging by the ________ he keeps, Mark must be an extremely wealthy man.

It’s ______ difficult to draw the boy’s attention to his lesson.