什么是暖风器？
参考答案：
暖风器是一种蒸汽--空气管式热交换器，管内流过由汽轮机引来的蒸汽，空气在管外通过时被加热。
She isn't here. She has to _____her baby at home. [ ]
A. look at
B. look like
C. look ater
D. look for
-2，4，-8，-4，32，28，( )
A．-464
B．896
C．664
D．148
