OFFICIAL EXPLANATION
Beating its wings 15 to 200 times per second, the hummingbird has the highest metabolism rate of any animal, excluding insects.A. its wings 15 to 200 times per second, the hummingbird has the highest metabolism rate of any animal, excluding insects
This answer choice makes correct use of the Superlative form (indicated here by the word highest).B. their wings 15 to 200 times per second, hummingbirds have highest metabolism rate of any animal, excluding insects
This answer choice is grammatically because of the misuse of the Superlative form indicated here by the use of the word highest. The adjective of a Superlative must be preceded by the word the. In this sentence, highest is preceded by have.C. its wings 15 to 200 times per second, the highest metabolism rate of any animal, excluding insects, belongs to the hummingbird
This answer choice is grammatically incorrect. The original sentence begins with a modifier: Beating its wings 15 to 200 times per second. A modifier should be placed right next to the noun it describes. The only noun that this modifier can logically modify is hummingbird. However, what immediately follows the modifier is metabolism rate and metabolism rate cannot beat its wings.
What helps us identify this question as a Dangling Modifier question as well as identify the mistake is the following Stop Sign:
A modifier, characterized by all of the following:
1. Verb+ing or Verb in 3rd form
2. Separated from the rest of the sentence by a comma
3. Appears at the very beginning of the sentence
Whenever you see this Stop Sign, focus on the modifier: check whether the noun right after the modifier is indeed the noun that the modifier describes. If it isn't - you've found your mistake.D. its wings 15 to 200 times per second, the hummingbird has a highest metabolism rate of any animal, excluding insects
This answer choice is grammatically because of the misuse of the Superlative form indicated here by the use of the word highest. The adjective of a Superlative must be preceded by the word the. In this sentence, highest is preceded by a.E. their wings 15 to 200 times per second, hummingbirds have the highest metabolism rate of any animal, not including the metabolism rate of insects
Although this answer choice is grammatically correct, it is stylistically flawed. The phrase not including the metabolism rate of insects should be replaced by the more concise excluding insects.