In strict 2PL all the exclusive locks must be unlocked after the commit operation.
Option (a) write operation in both schedules need exclusive locks,thus it is wrong option because it does not follows locking protocol
option(b) In S1 shared lock is unlocked after commit operation. So,wrong.
option (c) correct. Since, all exclusive locks in both S1 and S2 are unlocked after commit operation
option (d) exclusive locks are not unlocked after commit operation. So wrong.