Solution 2B This peep is inferior, because after W2 connects White has good shape, while B1 has only 3 liberties and no good followup.
Solution 2C This is the best peep, because when W2 connects B1is not only on White’s shape point but also still has all 4 of its liberties, and this can make the difference between winning and losing any later fight involving this Black stone. Of course if White should mistakenly answer at “a” instead of 2, then B“b” is available as a big Ko threat to force W2 after all, and that’s worse for White than this diagram. If W“b” in response to B1 it may be feasible and/or best to simply tenuki, leaving B1 behind as Aji, or it may be productive to reinforce it. But in any event, it was still ideally placed.