The following sentence has been split into four segments. Identify the segment that contains a grammatical error.

The mother as well as the sons / were asked to appear / before the magistrate / for interrogation. 

The erroneous part of the sentence is: were asked to appear

Key Points

• The error here lies in the Subject-Verb agreement.
• Subject-verb agreement is a grammatical rule that states that the subject of a sentence must agree in number with the verb.
• If the subject is singular, the verb must be singular, and if the subject is plural, the verb must be plural.
• In the given sentence "the mother" is a singular subject, the verb should be "was" instead of "were."
• The phrase "as well as" doesn't affect the subject-verb agreement; it is an additional element providing information about the subjects but doesn't change the singular nature of "the mother."

Therefore, the correct answer is option 1.

Corrected sentence: The mother as well as the sons was asked to appear before the magistrate for interrogation.