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

Ex Input:
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 Output:
The first period of the paleozoic era was called what?

Ex Input:
Passage: Physical properties include color, density, hardness, and melting and boiling points. Answer: physical

Ex Output:
Hardness, density, color, and melting and boiling points are all considered what types of properties?

Ex Input:
Passage: Biochemical reactions are optimal at physiological temperatures. For example, most biochemical reactions work best at the normal body temperature of 98.6F (37C). Many enzymes lose function at lower and higher temperatures. At higher temperatures, an enzyme's shape deteriorates, and only when the temperature comes back to normal does the enzyme regain its shape and normal activity. Answer: enzymes

Ex Output:
Biochemical reactions are optimal at physiological temperatures because many what lose function at lower and higher temperatures?