肝脓肿CT扫描所出现的“靶征”可以是
A．无环
B．单环
C．双环
D．三环
E．四环
参考答案：B,C,D
若函数f（x）=ax2+2x+5在（4，+∞）上单调递增，则实数a的取值范围是______．
Nowadays car owners complain about the traffic jam，but there is no sign that the number
of household cars would be________.[ ]
A．reduced
B．fallen
C．put down
D．cut off
