(2013·黑龙江双鸭一中月考)It was several years ________ I realized ________ David had lied to me.

A．when; that

B．that; when

C．before; that

D．until; why

下列关于打桩时桩身锤击拉应力的说法中，哪些是正确的（）。

A、锤击力波幅值低和持续时间长，拉应力就低

B、打桩时土阻力弱，拉应力就强

C、桩愈长且锤击力波持续时间愈短，最大拉应力位置就愈往下移

D、混凝土的动态抗拉强度一般比相应的静态强度高