OK, I feel really stupid for forgetting (d), but at the same time, (d) does not provide any great insight into the person answering.
You see if you answer (a), it means you have a big ego that emanates from your cock,
If you answer (b) it means you're insecure and are scared that other men will take your girls away (I'm looking at all you NTR haters out there - scared I tell you!).
Or (c) means you're comfortable with who you are and do not need to turn the lights out when being intimate.
Now if you choose (d), I think it means you are afraid to give away any details of your personality...
I may have had a few too many whiskeys tonight, but I do feel I'm being very insightful right now.