— How about this camera?
— It is too expensive. I can't afford it.
A:cheap
B:heavy
C:dear
下列属于人类对太阳能的间接利用的是 ( )
听下面一段对话,回答小题。
一个大池塘被正在生长的植物逐渐覆盖,每天新增的覆盖面积加倍,第9天池塘已被覆盖一半,那么大池塘全部被覆盖所需的天数是( )