I didn't think maths ______ important at that time. [ ]
A. is
B. were
C. are
D. was
答案:D
简述造礁珊瑚的形成条件。
作业前和作业时先检查作业范围内的()状况,并在有人监护下开始工作。
A、生产
B、安全
C、工作