sentences:  Most four-wheel-drive layouts are front-engined and are derivatives of earlier front-engine, rear-wheel-drive designs.The "mid-engine, four-wheel drive" layout (abbreviated as M4 layout) places the engine in the middle of the vehicle, between both axles and drives all four road wheels.Although the term "mid-engine" can mean the engine is placed anywhere in the vehicle such that the centre of gravity of the engine lies between the front and rear axles, it is usually used for sports cars and racing cars where the engine is behind the passenger compartment.