It is uncertain ___ side effects these weight-loss drugs will bring about, although hundreds of thousands of patients have taken it.

A．that

B．whether

C．how

D．what

螺旋筋柱的核心区混凝土抗压强度高于fc是因为（）。

A.螺旋筋参与受压

B.螺旋筋使核心区混凝土密实

C.螺旋筋约束了核心区混凝土的横向变形

D.螺旋筋使核心区混凝土中不出现内裂缝