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

[EX Q]: Passage: The most noticeable magnetic activity of the Sun is the appearance of sunspots. Sunspots are cooler, darker areas on the Sun's surface ( Figure below ). Sunspots occur in an 11-year cycle. The number of sunspots begins at a minimum. The number gradually increases to the maximum. Then the number returns to a minimum again. Answer: 11
[EX A]: What is the year cycle that sunspots occur?

[EX Q]: Passage: The first period of the Paleozoic Era was the Cambrian. By the beginning of the Paleozoic, organisms evolved shells. Shells could hold their soft tissues together. Shells could protect them from predators and from drying out. Some organisms evolved external skeletons. These are called exoskeletons . Organisms with hard parts also make good fossils. Fossils from the Cambrian are much more abundant than fossils from the Precambrian. Answer: cambrian
[EX A]: The first period of the paleozoic era was called what?

[EX Q]: Passage: 3. Electrical energy is the energy of moving electrons. Electrons flow through wires to create electric current. Answer: electric current
[EX A]:
Electrons flow through wires to create what?