Which of the following sentences uses correct grammar?

Answer: The correct answer is Option D. The sentence uses passive voice, which is the preferred way of writing technical reports in civil engineering. Passive voice emphasizes the action rather than the actor and it is more objective.
Explanation: Option A is incorrect because it has a redundancy of subject pronouns “The engineer” and “he”. Option B is grammatically correct but uses active voice, which is less preferred in technical writing. Option C is grammatically incorrect because it suggests that the plan is the one doing the explaining. Option D is grammatically correct and uses passive voice to emphasize the action of explaining the plan.