SatelliteDNA-卫星DNA
参考答案：
又称串联重复序列，由2~6个核苷酸组成的重复单位组成的串联重复。
76. All flights _______ called off because of the terrible weather, they had to go there by train.
A．were
B．had been
C．being
D．having been
将一铜球放入底面半径为4cm的圆柱形玻璃容器内，水面升高9cm，则这个铜球的半径为______cm．
