Identify the part of the sentence that has an error in it.
This is the only one (D)/ of his novels (B) that are (C) not worth reading. (D)

Correct option is A

Option (C) contains an error.
Correct sentence: This is the only one of his novels that is not worth reading.
Detailed Explanation (English):
The relative clause “that is not worth reading” refers to “the only one”, not to “novels.”
Since “the only one” is singular, the verb should also be singular (is) instead of plural (are).
Grammatical rule used:
When the antecedent (the word to which the relative clause refers) is singular, the verb inside the clause must also be singular.
Explanation of the grammatical rule in Hindi:
जब किसी relative clause (जैसे “that is…”) का संबंध किसी एकवचन संज्ञा से होता है, तो उसकी क्रिया भी एकवचन (singular) होनी चाहिए।
यहाँ “the only one” एकवचन है, इसलिए “is” का प्रयोग किया जाएगा, “are” का नहीं।
Example:
· This is one of the books that are worth reading. (Refers to books — plural)
· This is the only one of the books that is worth reading. (Refers to the only one — singular)