The sentence given in option (a) is erroneous. In that sentence, the use of a singular verb 'bands' is incorrectly used to denote the plural noun 'tribes' which leads to error in subject verb agreement. Instead, the plural form of the verb, i.e., 'band' is to be used. Other sentences are grammatically correct and meaningful.
Hence, the correct answer is option (a).
Note:
Subject-Verb Agreement: Matching up singular or plural subjects with singular or plural forms of a verb is part of the process called agreement. This can be understood better by the examples given: - "She likes cooking." [singular subject and verb] -- "They like to cook vegetables." [plural subject and verb]
Study Notes
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