Mrs. Brown was much disappointed to see the washing machine she had had ____ went wrong again.

A．it

B．it repaired

C．repaired

D．to be repaired

在原子吸收分析中，下列操作不能提高灵敏度的是（）

（A）增大灯电流

（B）无火焰原子化

（C）增大负高压

（D）减少光谱带