---Few young people in China know about Lady Gaga , _______?

---_______, she is quite famous here in China.

A．do they; No

B．do they; Yes

C．don’t they; No

D．don’t they; Yes

软水器运行时，当一级罐出口硬度超过（）时，需要再生。

（A）30mg/L

（B）40mg/L

（C）50mg/L