提升信号装置要求（）齐全。
A.声光
B.光
C.声
参考答案：A
—I have got a headache.
—No wonder. You ________ in front of that computer too long.[ ]
A. work
B. are working
C. worked
D. have been working
DAC钢制之模具淬火冷却方式不能为（）
A、油冷
B、空冷
C、高压气冷
D、水冷
