问题
选择题
There are several factors _______ in the economy _______ make it difficult to predict the future.
A．operate; where
B．operating; which
C．to operate; that
D．operated; what
答案
答案：B
本题考查非谓语动词及定语从句。名词factors与operate的关系为主动关系，用现在分词，后一空为定语从句，先行词为factors，在定语从句中作主语，故选B。