1.They have no choice but____.

1.They have no choice but____.
A.live on bread B.live by bread C.to live on bread D.to live by bread
2.Now we should do all we can ____the Great wall.
A.to prevent B.to preserve C.protect D.protest
3.It's no good ____.
A.waste a lot of time on nothing
B.to waste a lot of time on nothing
C.wasting a lot of time to complain
D.wasting a lot of time complaning
4.____the programme,they have to stay there for another 2 weeks.
A.Not completing B.Not completed C.Not having completed D.Having not completed
5.though___money,his parents managed to send him to university.
A.lacked B.lacking of C.lacking D.lacked in
6.the bell__the end of the period rang,___our heated discussion.
A.indicating;interrupting B.indicated;interrupting C.indicating;interrupted D.indicated;interrupted
这些题,,选什么,为什么选这个,还有其他选项为什么不对,