Question

which object is a compound machine? ramp bicycle knife screw

Explanation:

A compound machine is made up of two or more simple machines. A ramp is an inclined plane (a simple machine). A knife has a wedge (a simple machine). A screw is a simple machine. A bicycle is made up of multiple simple machines like wheels (levers/ wheels - and - axles), gears (wheels - and - axles/ pulleys in a sense), and the frame which can involve inclined planes in some parts.

Answer:

bicycle