1．(2012·安徽)I remembered________the door before I left the office, but forgot to turn off the lights.
A．locking B．to lock
C．having locked D．to have locked
答案：B 句意：我在离开办公室以前，记着了要锁门，但是忘了要关灯。remember to do sth.“记着要做某事”；remember doing sth.“记着做过某事”。由句意可知，B项符合题意。
2．(2012·北京)Birds' singing is sometimes a warning to other birds________away.
A．to stay B．staying
C．stayed D．stay
答案：A other birds与stay away之间是主动关系且根据句意“鸟叫有时候是警告其他的鸟儿离开。”可知选A项。不定式在此表示目的。
3．(2012·湖南)We've had a good start, but next，more work needs ________ to achieve the final success.
A．being done B．do
C．to be done D．to do
