Neither Mary nor her sisters knows where the book could have been placed. A. norB. knowsC. have been D. No Error

Let's analyze the sentence step by step to identify any errors:

1. "Neither Mary nor her sisters knows where the book could have been placed."

• "Neither...nor" is a correlative conjunction pair that is used correctly here to connect two subjects: "Mary" and "her sisters."

2. "knows" is the verb that follows the subjects connected by "neither...nor."

• The rule for subject-verb agreement with "neither...nor" is that the verb should agree with the subject that is closer to it. In this case, "her sisters" is closer to the verb "knows."

3. "her sisters" is plural, so the verb should be in the plural form to agree with it.

• The correct plural form of "knows" is "know."

4. "where the book could have been placed" is a dependent clause that is correctly placed and does not contain any errors.

Therefore, the error in the sentence is with the verb "knows." It should be "know" to agree with the plural subject "her sisters."

The correct sentence should be: "Neither Mary nor her sisters know where the book could have been placed."

So, the answer is: B. knows