疱疹性咽峡炎常见的病原体是（）
A.腺病毒
B.柯萨奇病毒
C.流感病毒
D.肠病毒
E.鼻病毒
参考答案：B
“Did he repair his bike all by himself that day?” “No, he ___.”
A．hadn't
B．had had it repairing
C．had it being repairing
D．had Jimmy do it
在电场中P点放一个检验电荷-q，它所受的电场力为F，则关于P点电场强度E，正确的说法是（ ）
A．E=Fq，方向与F相同
B．若取走-q，P点的电场强度E=0
C．若检验电荷为-2q，则E=F2q
D．E与检验电荷无关
