Which of these explains how a trench can form?
A: two oceanic plates converging

New vaccines for diseases are being developed all the time. How do vaccines most likely help people?
A: Vaccines help prevent illnesses.

Why is the ozone content of the stratosphere important to living organisms?
A: Ozone absorbs ultraviolet radiation from the Sun.

Which geologic feature is evidence that the North American plate once collided with the Eurasian and African plates?
A:
the Appalachian Mountains