My mother is _____ TV. [ ]
A. looking at
B. seeing
C. reading
D. watching
答案：D
体积为2×10-3米3的金属块浸没在水中。求金属块受到的浮力大小F浮。
当APU一个环路有故障（断路或无电源）.会影响到警告系统
