Hello Hirashin,
A1 = Completely acceptable.
A2 = Completely acceptable.
B1 = Understandable, but I don't think "occurs" fits here as well as "come to mind".
B2 = As above. Understandable, but not as elegant as just "come to mind". Somewhat redundant.
C1 = Understandable, but to me not as good of a choice as A1.
C2 = Not really the correct use of the phrase "come up with", and I think invalid in this situation.
C3 = Needs the addition of the word of.
C4 = Fine.
D1 = Comes to mind to - would be an unusual and, I think, invalid way to use that phrase.
D2 = Acceptable, but I think not nearly as good as A1, A2, or C4.