501.Ring me at 5 am?No.Better not so early!I _________.
I got it.
A.will sleep
B.sleep
C.am sleeping
D.will be sleeping
502.Because of the Russian gas limit to Europe,attempts ______ to use botanical fuel as a source of power.
A.have made
B.having made
C.are being made
D.will be making
501.答案是D;根据语境，此处at 5 am明显表示将来时间，那时将正在睡觉。
502.答案是C;此题根据语境推断，指现在的情况。Make an attempt to do sth./at doing sth.为固定短语:试图干某事。
