18. Substances change states when they move between solid, liquid, and gas forms. When a substance changes from one state of matter to another, it has undergone
A. a reduction in mass.
B. an increase in mass.
C. a chemical change.
D. a physical change.

Which describes how weathering and erosion are different? weathering is caused by water. erosion is caused by wind and ice. erosion transports sediments. weathering is a natural process.

In the african savanna,more wildebeests are born than the environment can support. which is most likely to happen over a period of years as a result

Consider darwin's first writings on the theory of natural selection. an important point of darwin's essay on the principle of population, written in 1798, was a peer's observation that in nature plants and animals produce far more offspring than can survive, this observation can be attributed to a) charles lyell. b) thomas malthus. c) jean-baptiste lamarck. d) johann friedrich meckel.