When is it cheaper to make an international call？
A. l0 a.m.
B. 5 p.m.
C. 11 p.m.
D. 8 a.m.
What can you do if the international line is engaged？
Ask the operator to call you back later.
B. Make a "person-to-person" call.
Call back outside office hours.
D. Wait and call again when the line is free.
生物生活的具体场所称为生境，又称栖息地。
A. 正确
B. 错误
【B16】
A. when
B. before
C. after
D. while
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