情绪和情感是人们工作和生活一种重要的交流方式，这种功能是通过（）来实现的。
A.身体姿势
B.表情
C.外在行为
D.语言
参考答案：B
His lecture _____ a wide range of topics and I cannot sum up what he said in a few sentences. [ ]
A. took
B. covered
C. referred
D. stated
A．时刻t线圈中电流的瞬时值icosωt
B．线圈中电流的有效值I
C．线圈中电流的有效值I=
D．线圈消耗的电功率P
cosωt
