Given a scientific passage and an answer, generate a question for the given answer.

Passage: Christopher Auyeung, using bat image by User:Rugby471/Wikimedia Commons. Bats use echolocation to identify the location of objects . CC BY-NC 3.0 (bat image available under public domain). Answer: echolocation
What do bats use to determine the location of objects?

Passage: It was known that DNA is composed of nucleotides , each of which contains a nitrogen-containing base, a five-carbon sugar (deoxyribose), and a phosphate group. In these nucleotides, there is one of the four possible bases: adenine (A), guanine (G), cytosine (C), or thymine (T) ( Figure below ). Adenine and guanine are purine bases, and cytosine and thymine are pyrimidine bases. Answer: nitrogen
What does the base of a nucleotide within dna consist of?

Passage: The Figure below shows the direction of the current that is generated by a moving magnet. If the magnet is moved back and forth repeatedly, the current keeps changing direction. In other words, alternating current (AC) is produced. Alternating current is electric current that keeps reversing direction. Answer: alternating current
What is the term for electric current that keeps reversing direction?