The professor,（ ）whether anyone would come to help him, had to prepare for the experiment by himself.
A、
did not know
B、
having not known
C、
had not known
D、
not knowing
【正确答案】：D
【题目解析】：
因为原句中有had to prepare（谓语动词）所以空格处应该为非谓语，不选A，非谓语否定的not要放在非谓语前面，不选BC，选D。句意：教授不知道是否有人会来帮助他，只好自己准备实验。
