Axon: the messenger cell that carries the command to contract muscles.
Each moon or planet matched to the most accurate characteristic;
1. It contains large amounts of frozen water - C. Europa
2. High levels of carbon dioxide increase the temperature of its atmosphere - B. Venus
3. It does not have enough gravity to have an atmosphere - A. Earth's moon
4. Astronomers believe there is a good chance it contains liquid water - D. Mars
Europa is the smallest of the four Galilean moons of Jupiter. Others are Io, Ganymede, and Callisto. An outer layer of water, about 100 km (62 mi) thick, covered the surface of Europa. A part of the outer layer (crust) is said to be frozen, while the other part is a liquid ocean below the ice.
Venus is the second planet from the Sun and the hottest planet in the solar system. The atmosphere of Venus is dense, and it is composed mainly of carbon dioxide (roughly 96.5 percent), which traps heat and causes a greenhouse effect.
