问题补充：
they visited our school, they showed great interest in everything they saw.
A. The first time
B. For the first time
C. At first
D. At the first time
答案：
(答案→)A. The first time
B. For the first time
C. At first
D. At the first time
解析：考查名词短语做连词，the first time+从句，第一次…,句意：他们第一次到我们学校，他们对看见的一切都感兴趣，For the first time是介词短语，不能接从句，at first介词短语，首先，不能接从句，选A。
