In addition to comets, water for Earth's early oceans might have come from

A. rain.

B. rivers.

C. cyanobacteria.

D. volcanic eruptions.

When magma cuts across another rock and hardens, resulting formation is called what?

Each Earth day is 24 hours long. Which statement explains why? A. It takes Earth 24 hours to rotate once on its axis. B. It takes the moon 24 hours to rotate once on its axis. C. It takes the moon 24 hours to complete one orbit of Earth. D.

A scientist should be willing to change his theory if the evidence does not support it. a. trueb. false

What term is used to describe artificial selection to obtain desired qualities in breeding pets and livestock? A. selective breeding B. negative selection C. survival of the fittest D. environmental selection

explain what happens at each of the different types of plate boundaries (divergent boundaries, convergent boundaries and transform boundaries)

Dams are often built to generate power. One negative impact of damming a river is reduced flow downstream water storage to battle a drought increased recreation opportunities flood control

What three cities form the global centers of economic activity?

Describe and explain the physical and/or chemical methods used to refine the coal

Explain the characteristics of authoritarianism, and identify two Central Asian countries that have this type of government

Why are the rivers so vital to europe's economy?