The sentence below has been divided into three parts. Select the part of the sentence that has an error. If the sentence has no error, select the option ‘No Error’.
In tropical and sub-tropical/ areas, malaria is one/ of the world’s biggest killer.

Correct option is D

• The phrase one of must be followed by a plural noun.
• Therefore, one of the world’s biggest killer is incorrect because killer should be plural: killers.