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)

To identify the grammatical error in the sentence, let's analyze each part step-by-step:

1. Analyzing the Verb "Know":
The verb "know" is a stative verb (or non-continuous verb). Stative verbs describe states of being, thoughts, emotions, or senses rather than physical actions or processes. Examples include know, believe, understand, love, and hate.

2. Grammar Rule for Stative Verbs:
Stative verbs are generally not used in continuous (progressive) tenses (like the present continuous: is/are + verb-ing). Instead, they are expressed in simple tenses (like the simple present tense).

3. Evaluating the Sentence Parts:
- "She is" (A): Correct subject and auxiliary verb combination.
- "knowing the answer" (B): This uses the present continuous form "is knowing" for the stative verb "know", which is grammatically incorrect.
- "to this question" (C): Correct prepositional phrase.
- "very well." (D): Correct adverbial modifier.

4. Corrected Sentence:
To make the sentence grammatically correct, the simple present tense "knows" should be used instead of "is knowing":
"She knows the answer to this question very well."

Therefore, the grammatical error is located in part (B).