“绿色化学”是21世纪化学的主导方向，其核心是利用化学原理从源头上消除污染，你认为符合“绿色化学”，对人类的生存环境不会造成危害的是[ ]

A.随意丢弃废弃电池

B.任意排放生活污水

C.用氢气作燃料

D.汽车排放出有害废气

— I'm really confused on how to balance my interest and study.

— Well, turn to your teacher for advice, in my opinion, _____ you'll make it. [ ]

A. but

B. and

C. so

D. unless