Step 1: Understand the question
We are asked to identify the incorrect sentence. The given correct option is (C): "The king with all his sons were imprisoned." We need to analyze why this sentence is wrong grammatically.
Step 2: Subject-verb agreement rule
In English grammar, the verb must agree in number with the subject. Here the main subject is "The king," which is singular. The phrase "with all his sons" is a prepositional phrase that adds extra information, but it does not change the number of the subject. Therefore, the verb should remain singular to agree with "The king."
Step 3: Error in the sentence
The sentence says: "The king with all his sons were imprisoned."
The verb "were" is plural and incorrectly agrees with "sons" instead of the true subject "king."
Step 4: Corrected version
The correct sentence should be: "The king with all his sons was imprisoned."
Here, "was" correctly matches the singular subject "king."
Step 5: Final justification
Thus, the incorrect sentence is (C) because of a subject-verb agreement error. The main subject is singular, so the verb must also be singular.
Final Answer: The correct option is (C) The king with all his sons were imprisoned, which should be corrected to "was imprisoned."