下列分子式分别代表什么物质。
COS
参考答案：
羰基硫
Of all the students in our class. Betty writes _____.[ ]
A. very carefully
B. more carefully
C. most carefully
D. the most careful
______________ Do you know where the post office is?[ ]
A. Hey!
B. Hello!
C. Look!
D. Excuse me.
