Question

what is an engine compression stroke?
a) when the piston moves down drawing air and fuel into the cylinder.
b) when the piston moves up causing the air/fuel mixture to compress.
c) when the spark plug ignites causing compression to occur.
d) when the piston moves up forcing the exhaust to compress.

Explanation:

In an engine, during the compression stroke, the piston moves upwards. This action compresses the air - fuel mixture inside the cylinder. Option A describes the intake stroke, option C describes the power stroke where ignition occurs, and option D is incorrect as the exhaust is not compressed during the compression stroke.

Answer:

B. When the piston moves up causing the air/fuel mixture to compress.