What happens during the intake stroke of a four-stroke internal combustion engine?

Question

A. The piston moves downward, creating a partial vacuum that draws in air and fuel.
B. The piston moves downward as a result of the air/fuel mixture doing work on it.
C. The piston moves upward, compressing the air/fuel mixture and raising its temperature.
D. The piston moves upward, doing work on the air/fuel mixture to push it out of the cylinder.

Answer 1

https://en.wikipedia.org/wiki/Four-stroke_engine

Answer 2

A. The piston moves downward, creating a partial vacuum that draws in air and fuel.