求助 新prep sc2---166

zxppx

1.     what引导的名词性从句做主语时，主句谓语动词的单复数情况：
(1)What在从句中做主语，主句谓语由what从句的谓语决定。
             1) What is difficult to understand is A.；What are difficult to understand are A and B.
(2)what在从句中做宾语，主句谓语由主句表语/宾语决定what they want are XX,XX&XX。
2) What his father left him are a few English books.
这道题中，what is more difficult to determine中what是作为主语，所以主句中的谓语由what从句中的谓语is决定，即is