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Solution

Statement I:

Conservative $2PL$ means Conservative Two Phase Locking.

In this protocol, a transaction obtains all required locks before it starts execution.

If all locks are not available, the transaction does not start.

Because a transaction does not hold some locks while waiting for other locks, circular wait cannot occur.

So, Conservative $2PL$ is deadlock-free.

Therefore, Statement I is true.

Statement II:

Thomas's write rule is a modification of timestamp ordering.

It allows some obsolete write operations to be ignored.

Because of this, it can generate schedules that are view serializable but not necessarily conflict serializable.

So, Thomas's write rule does not enforce conflict serializability.

Therefore, Statement II is false.

Statement III:

Timestamp ordering protocol assigns a timestamp to every transaction.

The serial order of transactions is decided according to their timestamps.

So, it ensures serializability based on the timestamp order.

Therefore, Statement III is true.

Hence, Statement I and Statement III are true, and Statement II is false.