You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
Given a scientific passage and an answer, generate a question for the given answer.

Passage: A frameshift mutation is a deletion or insertion of one or more nucleotides that changes the reading frame of the base sequence. Deletions remove nucleotides, and insertions add nucleotides. Consider the following sequence of bases in RNA:. Answer: nucleotides.
Solution: A frameshift mutation is a deletion or insertion of one or more of what that changes the reading frame of the base sequence?
Why? The science passage defines frame mutation and the main compoment here is nucleotides. Hence the generated question is apt.

New input: Passage: Animals such as bats and dolphins send out ultrasound waves and use their echoes, or reflected waves, to identify the locations of objects they cannot see. This is called echolocation. Animals use echolocation to find prey and avoid running into objects in the dark. You can see in the Figure below and also at the following URL how a bat uses echolocation to find insect prey. http://www. bsos. umd. edu/psyc/batlab/headaimmovies/nsf_challenge/nsf4. wmv. Answer: echolocation
Solution:
What is the term for the method of sending out ultrasound waves to determine the locations of objects?