In an internal combustion engine, the gas vapor/air mixture enters the cylinder during the stroke.
O intake
O compression
O power
O exhaust

i think the answer is a, hope this : )

truck y has a greater velocity than truck x.

igneous rocks also form where plates converge. the subducting plate melts as it sinks into the crust of the earth, and the melt rises into the overriding plate forming volcanoes. metamorphic rocks are formed mainly in the lithosphere, wherever there is high pressure and high temperature. -woods