Well, in the first question, the second option is the correct. That's what we call ''Ênclise''. ''Ênclise'' is the way to organize ''Pronomes''. In the first case, the letter B is correct because that doesn't have any ''Locução'' to bring the ''Pronome'' next to him.(THIS SOLUTION IT'S ONLY FOR INTERROGATIONS). Example: ''Por que ME abandonas?'' Now is showing up the ''Locução'' without ''PODE'' like your question was. ''Por que pode abandonar-ME?'' With the presence of the ''Verbo Auxiliar'', things can change a little. ''Por que deve abandonar-ME?'' Now, It's clear that difference. Obs.: But these examples in you questions, all of them are correct and understandable.