Thomas write rule says : " It states that, if a more recent transaction has already written the value of an object, then a less recent transaction does not need perform its own write since it will eventually be overwritten by the more recent one. "
as transaction T1 has started execution before the Transaction T2 then the schedule is allowed under Tomas write rule.
Basic timestamp rule says : " the transaction started before the object's write timestamp it means that something changed the object's data after the transaction started. In this case, the transaction is canceled and must be restarted. " so T1 is started R1(A) before W1(A) hence it is canceled . This schedule is Not allowed under Basic timestamp protocol
hence option B is correct .