—Your colleague is speaking English with fluency.

—It's no wonder．She ____ in the UK for a year as a visiting professor

A．worked

B．has worked

C．had worked

D．has been working

(5分)下列化学用语书写均有错误，请你加以改正。

①2个氮分子：2N     ；②l个钙离子：Ca⁺²    ；③氖气：Ne₂    ；

④氯化镁：MgCl      ；⑤氧化铁中铁元素的化合价：₂0₃      。