Remark
No wonder you are confused!!
The problem is that you are probably given some background information in your notes that came with this problem. Without the notes, the best I can do is guess. Let's just list the choices we are given.
Discussion
A: This does not sound like it could be interpreted as any kind of irony. All he is doing is sitting and contemplating something else while he rubs his temples.
B: I don't think you can construe B as ironic unless the General is one of those people that is very careful how he dresses. The professor is very casual when you compare him to the General. I'm not sure it is irony however.
C: This answer sounds very possible. The speaker is contrasting a very serious sentence that he heard last night. The irony is that he was paying absently with dice when the revelation came. The contrast (dice and an important sentence revealed to him could be very ironic). The irony is that Barnhouse discovered his unique power of mind over matter when he threw 7 sevens in a row. The student/narrator also developed powers when paying with the dice.
D. This is just an usual event. It is not ironic, unless there is more to it than we know about just from reading it.
