The sentence that has illogical comparison is the second example - A parrot's feathers are more colorful than a parakeet. It should be ... than a parakeet's.
The correct answer is B. A parrot's feathers are more colorful than a parakeet.
Explanation:
An illogical comparison is when two different elements that do not belong to the same group or category are compared in a sentence, this makes the comparison invalid as you can only make a valid comparison by comparing two elements of the same kind and therefore the illogical comparison is not correct during speech or writing. Additionally, this type of error in comparison emerges mainly as a result of issues on the grammatical construction of sentences.
This is the case of the sentence "A parrot's feathers are more colorful than a parakeet." the elements that are being compared are not of the same kind, in this sentence the feathers of a parrot are being compared to a parakeet which means the author is trying to compare the features of an animal to an animal which makes no sense or is illogical. Instead, for the sentence to stop having an illogical comparison the sentence can be changed to "A parrot’s feathers are more colorful than a parakeet's" or "A parrot’s feathers are more colorful than those from the parakeet". Thus, the sentence that has an illogical comparison is the sentence "B", as this sentence is comparing two elements of different kinds which is illogical and grammatically wrong.
