问题
选择题
The room _____, but now it's dirty again. [ ]
A. was cleaned
B. is cleaned
C. cleaned
D. cleans
答案
答案：A
搜题请搜索小程序“爱下问搜题”
The room _____, but now it's dirty again. [ ]
A. was cleaned
B. is cleaned
C. cleaned
D. cleans
答案：A
sin100πt （V）的 正弦交流电源，图中电流表内阻不计．副线圈接入“110V，60W”灯泡一只，且灯光正常发光．下列说法正确的是（ ）
/22 A