OG 211

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（B）

(E) are established by carbon-14 dating, but that which is much more difficult to determine is

Two instances of subject-verb agreement must be observed in this sentence: The period... has been established and what is much more difficult to determine... is. Both clauses have singular subjects and must have singular verbs. Only B, the best choice, observes these requirements. A incorrectly uses the plural form are in the second clause. Choices C and D incorrectly use the plural form have in the first clause, and D incorrectly uses are in the second clause as well. E incorrectly uses the plural form are in the first clause. Furthermore, because the date of the period in question was established before the writing of the sentence, the verb of that clause must be in the present perfect form (has been established).

我觉得DETERMINE 后面应该用ARE呀,因为后面并列的几项都是主语,自然应该用复数形式呀?谁能帮帮我?

我的观点，what句子作主语后只能用单数，但如what单独作主语，则看后，如what are  these objects?

如果是reason for加三个东东，则reason for the meaning意思上难理解。

第二句话，我同意；

第一句话，我觉得应该是what 从句作主语时，主句的单复应该与 what 从句一致。

笨鸟语法手册说~~

what 从句做主语时，主句的谓语动词形式由后面的名词决定；如果what在what从句中做主语，它的谓语动词形式应该与主句的谓语动词形式保持一致。/主语从句做主语只有这个例外，其他的都用单数谓语。

蓝色的什么意思啊??

此外，og说：Furthermore, because the date of the period in question was established before the writing of the sentence, the verb of that clause must be in the present perfect form (has been established).

可period的修饰语when……是were过去时啊？people后不要用过去完成时吗？？

这个句子可以简化成the period has been established，people及其前面的乱七八糟的东西都是修饰period的，当然用过去式。用现在完成时或者过去完成时，要看establish发生是在过去某个时间点之前还是在现在之前。