Choose the part of the sentences which has an error :

Question

Accepted Answer

The correct option is 4:

The error lies in the use of the preposition "by" in the phrase "covered by feathers." In standard English usage, when describing what covers the surface of something, especially a natural covering, the preposition "with" is almost universally preferred over "by." Birds' bodies are physically covered *with* feathers, indicating the material that forms the layer. The preposition "by" is typically reserved for indicating the agent (the doer of an action in a passive voice construction), which is not the case here, as the feathers are the covering, not the agent performing the covering action. The correct phrasing is, "Birds are warm-blooded vertebrate animals whose bodies are covered with feathers."

The incorrect option is 1: This part, "Birds are warm-blooded vertebrate animals," is grammatically sound. It correctly introduces the subject ("Birds") and describes their biological classification using accurate adjectives and nouns. The verb "are" correctly agrees with the plural subject "Birds."

The incorrect option is 2: The relative clause introduction, "whose bodies are," is correct. "Whose" is the appropriate possessive relative pronoun linking the characteristic of the bodies back to "Birds." The plural subject "bodies" correctly uses the plural linking verb "are."

The incorrect option is 3: The phrase "vertebrate animals" is part of the introductory descriptive phrase in Option 1, even though it is listed separately here. Assuming the full phrase is "Birds are warm-blooded vertebrate animals," this part is factually correct in its description of birds and grammatically correct as the object of the predicate.