Given a scientific question, generate a correct answer to it.

[Q]: If no unbalanced force acts on an object the object remains at constant velocity or what?
[A]: at rest

[Q]: Would you find cells that contain a cell wall, a large central vacuole, and plastids in plant or animal cells?
[A]: plant cells

[Q]: What is it called when two waves in the same medium pass one another?
[A]:
interference