A:he was able to make himself hear
B:was he able to make himself hear
C:was he able to make himself heard
D:he was able to make himself heard
函数f(x)=sin(﹣2x)的一个递增区间是( )
甲坐在人民大会堂台前60 m处听报告,乙坐在家里离电视机5 m处听电视转播,已知乙所在处与人民大会堂相距1 000 km,不考虑其他因素,则(空气中声速为340 m/s)( )