从所给的四个选项中，选择最合适的一个填入问号处，使之呈现一定的规律性。（）
A.选项A
B.选项B
C.选项C
D.选项D
参考答案：C
—Excuse me. Could you tell me _______?
—Yes, There is a video shop next to the tall building. [ ]
A. where can I buy some CDs
B. where I can buy some CDs
C. when can I buy some CDs
D. when I can buy some CDs
萤石的主要成份是（），它的熔点较低。
