20. Which of the following is grammatically accurate?
(A) Malvin Gray Johnson is noted especially for the pictures who he painted in Brightwood, Virginia, in the late summer of 1934.
(B) Successful economists must be able understand the effect of world events on national economies.
(C) The distinction between complex and simple lipids lie in their cell structure.
(D) The fundamental problem of a tax system is to collect enough money to pay for the expenses of government.

(A) Malvin Gray Johnson is noted especially for the pictures who he painted in Brightwood, Virginia, in the late summer of 1934.

• 這個選項中的錯誤在於使用了 "who" 來指代 "pictures"。應該使用 "that" 或 "which" 來修正這個句子。

(B) Successful economists must be able understand the effect of world events on national economies.

• 這個選項缺少了 "to"，應該是 "must be able to understand"。

(C) The distinction between complex and simple lipids lie in their cell structure.

• 這個選項的主語是 "the distinction"（單數），因此應該使用單數動詞 "lies" 而不是 "lie"。

(D) The fundamental problem of a tax system is to collect enough money to pay for the expenses of government.

• 這個選項的語法結構正確，沒有明顯的錯誤。

因此，選項 (D) 是語法正確的句子。