In the following question, a sentence is divided into four parts. Choose the part of the sentence which may contain a grammatical error in it. If all the parts of the sentence are grammatically correct and contextually meaningful, choose option “No error” as the answer choice.
She is (A)/ knowing the answer (B)/ to this question (C)/ very well. (D)

The correct option is B.

Detailed Explanation:
Let us analyze the given sentence by breaking it down into its constituent parts:
"She is (A)/ knowing the answer (B)/ to this question (C)/ very well. (D)"

The grammatical error lies in part (B) of the sentence.
The verb "know" is a stative verb. Stative verbs describe a state of being, opinion, belief, or knowledge rather than a dynamic action. Other examples of stative verbs include understand, believe, remember, and love.
Under standard grammatical rules, stative verbs are not used in continuous (progressive) tenses (such as "is knowing"). Instead, they must be used in their simple tense forms.

Therefore, the present continuous phrase "is knowing" must be replaced with the simple present tense "knows" to agree with the singular subject "She".

The grammatically correct sentence is:
"She knows the answer to this question very well."