水痘的潜伏期为()
A．1～3天
B．3～5天
C．5～7N
D．7～10天
E．10～21天
参考答案：E
已知抛物线y=ax2+2ax+4（0<a<3），A（x1，y1），B（x2，y2）是抛物线上两点，若x1>x2，且x1+x2=1-a，则 [ ]
A．y1<y2
B．y1=y2
C．y1>y2
D．y1与y2的大小不能确定
The parents felt helpless when they found their son had ____ love stories for long.
[ ]
A. addicted
B. addicted to
C. addicted himself
D. been addicted to
