Select the most appropriate option to improve the bold part of the sentence.
Had I known about the delay, I will wait.

Correct option is A

The correct substitution of the highlighted words is (a) would have waited.
Explanation: This is a third conditional (unreal past condition). With Had I known (inverted past perfect = If I had known), the main clause takes would have + V³. Hence, “Had I known …, I would have waited.” “Will” is incorrect because the condition is counterfactual and refers to the past.
Grammatical rule used:
· Third conditional: If + past perfect, would/ could/ might + have + V³.
· Inversion (formal): Had + subject + past participle, omit if.
Example: Had she left earlier, she would have caught the train.
Information booster: After Had + subject + V³, never use will/would + V¹ for past hypotheticals; use would have + V³.