题目内容：
An A4 sized panel ( 太阳能板 ) put onto the back of a jacket costs __________ US$15. It could __________ a cellphone during a summer walk.
A. at most; work
B. at least; control
C. at least; fuel
D. at most; charge
参考答案：【答案仅供学习，请勿对照自行用药等】
答案解析：