Have you noticed the problem ___ he is now in low spirit ? ____ come?

A．where, What

B．that, How

C．in which, For

D．what, As

下列关于巨幼细胞贫血的描述，错误的是

A．是一种大细胞性贫血
B．是一种小细胞低色素性贫血
C．由叶酸缺乏引起者最多见
D．由维生素B₁₂缺乏引起者多为因子缺乏所致
E．可表现为“牛肉舌”