c - Cut-and-shut
Cut-and-shut - This is the practice of welding together separate halves of two cars to make one. This is extremely dangerous, and it is illegal to repair a car to below satisfactory quality. Things to watch out for are weld marks in the floor of the car and uneven gaps between panels and around the doors.
Also carefully check the car's documentation and make sure the chassis and engine numbers all match those on the registration document and MoT certificate.