People whose brains do not produce enough dopamine often ____ motivation.
A. lack of
B. are lacking in
C. lacking in
D. are lack
解答给B，但为什么还要be动词呢？
谢谢大神解惑

为什么不是lack？我也有同样疑问

lack是及词动词，不需有of

lack 当名词时才加 of

No one talks like that irl

我是说选项怎么不直接出一个“lack”就好

个人理解：因为这一句“whose brains do not produce enough dopamine”是people的名词子句，里面的动词并不是原句子主词people的。所以当这里的lack当形容词用的时候，遮住whose带领的那段名词子句，people are lacking in....这样就合理了。