Correct option is A
Option (a) contains an error.
· The correct phrase should be "might be the best," correcting the order of words for proper syntax.
· The modal verb "might" should be followed by the base form of the verb "be," and then the adjective "good" to correctly modify the noun "cook."
· The sentence should read "We are assured of the fact that Siben might be the best cook to prepare chicken curry for our lunch."
Grammatical rule used: Adverb placement is crucial in maintaining the grammatical structure and meaning of a sentence. The adverb "good" should appropriately modify the verb "be," and its placement directly before "be" is the standard structure in English.
Example: She could easily be the best dancer in the competition. (Here, "easily" correctly modifies "be").