OG211

[CUGGYER]

211. The period when the great painted caves at Lascaux and Altamira were occupied by Upper Paleolithic people has been established by carbon-14 dating, but what is much more difficult to determine are the reason for their decoration, the use to which primitive people put the caves, and the meaning of the magnificently depicted animals.
(A) has been established by carbon-14 dating, but what is much more difficult to determine are
(B) has been established by carbon-14 dating, but what is much more difficult to determine is
(C) have been established by carbon-14 dating, but what is much more difficult to determine is
(D) have been established by carbon-14 dating, but what is much more difficult to determine are
(E) are established by carbon-14 dating, but that which is much more difficult to determine is

答案B

主謂一致：what 從句做主語時，主句的謂語動詞形式由後面的名詞決定；如果what在what從句中做主語，它的謂語動詞形式應該與主句的謂語動詞形式保持一致。/主語從句做主語只有這個例外，其他的都用單數謂語。

我不太懂這句話的意思
我原本以為關代當主詞的句子 就是應該接單數動詞
他說動詞要跟著後面名詞來決定
那這題後面是 the reason ,the use and the meaning
不就要用複數名詞了嗎><

[Pufa]

what is much more difficult to determine is....

粗體字就是is的主詞哩。
what子句把後面的the reason, the use, and the meaning看成一個主體了。

如果改成：
what are much more difficult to determine are....
我想也是對的。

[CUGGYER]

也就是說 what 開頭的主詞 也有可能會有複數動詞嗎??

那延伸到which that開頭的主詞 也是相同的原則嗎?