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【单选题】Some of the most popular attractions across America are the many free concerts offered to public throughout the year. These involve not only amateur performers, but professional artists as well. The p...
A.
have the necessary facilities
B.
call attract more visitors
C.
want to serve the public
D.
are in a position to invite musicians
【多选题】符合短声的特点有（）。
A.
时程为数十至数百毫秒的纯音段；
B.
周期数固定、外包络呈菱形的一段正弦波；
C.
脉宽为50~200µs的矩形电脉冲；
D.
时程长短取决于冲击脉冲的宽窄；
E.
时程长短取决于耳机的频响特性。
【单选题】Some of the most popular attractions across America are the many free concerts offered to public throughout the year．These involve not only amateur performers, but professional artists as well．The pub...
A.
have the necessary facilities
B.
call attract more visitors
C.
want to serve the public
D.
are in a position to invite musicians