问题补充：
a difficult situation, so you should send him a message and give him some advice.
A. As he is in
B. He is in
C. Being in
D. He being in
答案：
A. As he is in
(答案→)B. He is in
C. Being in
D. He being in
解析：so（因此）是并列连词，引出一个表示结果的分句，前面应是一个表示原因的分句，则无需再用连词，排除A；C和D又不是句子，也排除，故选B。
