题干
—Why did she ______ your invitation?
—Because she had an important meeting to attend that day.
A：turn down
B：put away
C：look up
D：hand in
答案(点此获取答案解析）
A
转动，线圈中产生的交流电动势e随时间t变化的情况，如图所示，下列说法中正确的（ ）