Which of the following concurrency protocol ensures both conflict serializability and freedom from deadlock :

Explanation

2-phase locking is a concurrency control method that guarantees serializability, but because transactions may block one another while holding locks, 2PL can lead to deadlocks. Timestamp-based (time phase) ordering is a non-lock concurrency method: it ensures conflict serializability and no deadlock can occur since no transaction ever waits. So the answer is (b) II only.