请教8老师有关入籍的几个问题。

My friend Qian is working for CISCO. The company is planing to send him to work in China for up to year.

Qian is a green card holder. He has submitted citizenship application a few months ago. Also, he married a few month ago and his wife is currently in China. 

Qian would like to know the following:

1) What will  happen to his citizenship application if he decide to work in China for a few months or up to a year?

2) What does he need to do to keep his greencard while working in China?

3) Qian's wife want to apply for B Visa to come to the U.S. and join Qian. Somebody told Qian that if he go to work in China, his wife's chance of getting B2 visa will be higher than if he remains in the US. Is that true?

Thank you!