问题
选择题
—Why didn't you answer my phone when I phoned you at about 11 p. m. yesterday?
—I ___________and failed to hear the phone.
A．might have slept
B．must be sleeping
C．might be sleeping
D．must have been sleeping
答案
答案：D
本题可以采用排除法。问句中提供整个过程表示过去的行为。情态动词后接完成时表示对过去的猜测，故排除B、C。问句中有“at about 11 p．m．”具体的时间点，所以选D。