Question

When fuel and air are compressed in the compression stroke, ...... a. each molecule of fuel is heated to its flash point b. each molecule of air is heated to its flash point c. the exhaust valve opens to release excessive pressure

Answer 1

None of the choices is an appropriate response.

There's no such thing as the temperature of a molecule.  Temperature and
pressure are both outside-world manifestations of the energy the molecules
have.  But on the molecular level, what it is is the kinetic energy with which
they're all scurrying around.

When the fuel/air mixture is compressed during the compression stroke,
the temperature is raised to the flash point of the mixture.  The work done
during the compression pumps energy into the molecules, their kinetic
energy increases, and they begin scurrying around fast enough so that
when they collide, they're able to stick together, form a new molecule,
and release some of their kinetic energy in the form of heat.