This kind of thing is really common for transfers. If you have not heard back yet from B, and you would be happy to transfer to A, then accept the offer and pay the deposit at A before A’s cut off date. Then if B does offer you a space, you can decide if you prefer B to A. If you do decide to accept B, you deposit at B before their cut off date, and you let A know that your plans have changed. A will probably keep your deposit, but Oh well.
If C, D, and E are also in the running, you can repeat this cycle pretty much up until the first day of class if you want or need to.