Spent far too long looking for a pattern.
Working on first letter,
A A both have one ball inside circle
B B both have two balls inside
C has three balls inside
so answer is a C type, so either CX or CV
Looking at the second letter,
V V the circle is cut five times by squiggly lines.
X nine cuts
? has nine cuts so a X
answer CX = b, correct but I'm not convinced.
Wasted a lot of time looking at patterns of white and black balls inside/outside and number of balls and "enclosures" caused by squiggly line crossing circle. Not a thirty second question!