分馏塔共分为二段，上段为（），下段为（）。
A、精馏段；提馏段
B、精馏段；脱过热段
C、脱过热段；提馏段
参考答案：B
下列哪些疾病状态下，患者的血清TSH浓度常升高（）
A.Graves病
B.甲状腺腺样瘤
C.垂体腺瘤
D.异源性TSH综合征
E.甲状腺性甲减
His writing is so confusing that it's difficult to make out ________ he is trying to express.
A．what is it
B．what is it that
C．what is that
D．what it is that
