严冬青蛙要进入冬眠，影响青蛙这种行为的环境因素是（）
A、阳光
B、水分
C、温度
D、盐分
参考答案：C
She returned home , ______ the feathers_____ her chicken by the terrible tornado.
A．found; taken off
B．finding; had been taken off
C．to find; were taken away
D．finding; has been taken off
发动机尾气排放有黑烟，可能是哪个传感器的故障（）.
A.节气门位置传感器
B.发动机工作温度传感器
C.曲轴位置传感器
D.空气流量
