You should avoid options A and B. Here's why:
A. Telling him how concerned you are about him may seem like it would embarrass him, but it's important to express your concern in a supportive way. Avoiding this conversation can make him feel more isolated.
B. Leaving him alone to work it out is not a helpful approach. People dealing with depression and suicidal thoughts often need support and connection, not isolation.
C. Telling an adult you trust about the situation can be a very responsible action, as they may be able to provide the necessary help and resources.
D. Listening carefully to what he has to say is crucial in supporting a friend who may be struggling.
In summary, the best actions involve showing concern, offering support, listening, and seeking help from trusted adults.