Option A provides the clearest and most unambiguous notice because:

It explicitly references the relevant Sub-Clause (8.1) that governs Commencement Date notification.

It uses precise language “I hereby give notice” indicating formal notification.

It clearly states the Commencement Date with a specific date (17 April 2023).

Options B and C are less formal or ambiguous and do not refer to the proper contract clause, which could lead to disputes. Option D incorrectly refers to the Time for Completion start rather than the Commencement Date specifically.

Clear and formal notices help prevent contractual disputes by explicitly identifying the contractual clause and key date.