不属于第二信使的是______
A．垂体激素 B．cAMPC．cGMP D．Ca2+E．磷脂酰肌醇
参考答案：A
A kite made of silk _____ easily in weather with rain and strong winds. [ ]
A. isn't tom
B. doesn't tear
C. won't be torn
D. can't tear
显微镜放到实验桌上的正确位置是 ( )
A．实验者的正前方，镜筒朝后
B．实验桌的中央，镜筒朝前
C．最接近光源的地方
D．实验者的前方略偏左(距台边7厘米左右)，镜筒朝前
