Water is unique because

a. it is light enough to escape earth's gravity, but it has not done so

b. it exists in three different states at normal conditions in the earth's atmosphere

c. its molecules are in motion even when it is solid

d. it forms from a wide range of chemical processes

e. it contracts when it becomes gas

b. It exists in three different states at normal conditions in the Earth's atmosphere

Explanation:=

Snow, rain and water vapour can exist at normal conditions in the Earth's atmosphere.

a. is wrong. Only hydrogen and helium can escape Earth's atmosphere in significant amounts.

c. is wrong. The molecules of every substance are in motion even when it is solid.

d. is wrong. Other substances can form from a wide range of chemical processes.

e. is wrong. All substances expand when they become a gas.