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

Ex Input:
Passage: Restriction enzymes or restriction endonucleases are prokaryotic enzymes that recognize and cut DNA at specific sequences, called restriction sites. It is believed that they evolved as a defense mechanism against foreign DNA, such as viral DNA. Over 3,000 restriction enzymes have been identified. Some of the more common restriction enzymes are shown in the table below, where up and down arrows show the sites of cleavage. Restriction enzymes are named based on the prokaryotic organism they are isolated from. For example, those isolated from Escherichia coli would begin with Eco. As the Table below shows, digestion with the restriction enzymes will result in overlapping or blunt ends. EcoRI produces overlapping "sticky" ends: the enzyme cleaves between the G and A on both strands. On the other hand, SmaII restriction enzyme cleavage produces "blunt" ends. The enzyme cleaves between the G and C on both strands. Answer: dna

Ex Output:
Restriction enzymes or restriction endonucleases are prokaryotic enzymes that recognize and cut what at specific sequences?

Ex Input:
Passage: Air movement takes place in the troposphere. This is the lowest layer of the atmosphere. Air moves because of differences in heating. These differences create convection currents and winds ( Figure below ). Answer: troposphere

Ex Output:
What is the lowest layer of the atmosphere called?

Ex Input:
Passage: The two parathyroid glands are located behind the thyroid gland. Parathyroid hormone helps keep the level of calcium in the blood within a narrow range. It stimulates bone cells to dissolve calcium in bone matrix and release it into the blood. Answer: thyroid

Ex Output:
The two parathyroid glands are located behind what gland?