问题
选择题
Why pleasant smells do not reduce pain in man is a question still _______ by scientists.
A．answered
B．being answered
C．to be answered
D．that answered
答案
答案：C
考查非谓语动词。句意：为什么令人愉快的气味不能降低人的痛苦仍是科学家要回答的问题。根据语境看问题还没被解决所以用不定式的被动式做a question的定语。