目前有那些主流操作系统Windows、()、()。
参考答案:Unix;Linux
—You're supposed to hand in the travel diary as soon as possible.
—I see. I'm going to _______ until 11:30 pm once more.[ ]
A. cheer up
B. put up
C. turn up
D. stay up
承受动力作用的设备基础,一般应留施工缝。( )