._________life began on the earth is one of the biggest puzzles to scientists.
A.How | B.What | C.Where | D.That |
The teacher asked us ________ in our reports before class.
A.hand | B.to hands | C.handed | D.to hand |
Tom was the first ________ he was wrong.
A.admit | B.to admit | C.of admitting | D.for admitting[ |
—Send me an email when you are free, will you?
—________.
A.I must | B.I will | C.I can | D.I should |
Many students are ________ chatting online, which wastes them plenty of time.
A.crazy about | B.connected with | C.worried about | D.anxious about |
The crowd ________ eastward, believing that they can find gold there.
A.are headed | B.is headed | C.heads | D.are heading |