You will be given a definition of a task first, then some input of the task.
Given a scientific passage and an answer, generate a question for the given answer.

Passage: The main reason that insects have been so successful is their ability to fly. Insects are the only invertebrates that can fly and the first animals to evolve flight. Flight has important advantages. It's a guaranteed means of escape from nonflying predators. It also aids in the search for food and mates. Answer: insects
Output:
What are the only invertebrates that can fly?