Which suffix changes the meaning of memory to "to commit to memory"? - ize - able - al - ies

The correct answer is "-ize."

For example, I must "memorize" my vocabulary words before the test (I must "commit to memory" my vocabulary words ...). On the other hand, "memorable" means that something is able to remembered, the suffix - al means "pertaining to" (natural--pertaining to nature), and the suffix - ies simply changes certain words to plural meanings (party, parties).