Final answer:
In a supercell thunderstorm, a tornado typically develops on the boundary between the rear flank downdraft and the forward flank downdraft.
Step-by-step explanation:
In a supercell thunderstorm, the development of a tornado typically takes place on the boundary between the rear flank downdraft (RFD) and the forward flank downdraft (FFD). The RFD is a downdraft occurring at the back of the thunderstorm and is responsible for wrapping around and tightening the circulation near the surface, which may lead to tornado formation. The FFD, on the other hand, is located at the front of the storm and contains heavy precipitation. The interaction and wind shear between the RFD and the FFD can contribute to the vertical tilting of the horizontal rotation, facilitating the creation of a tornado.
The correct answer to the question is therefore: (b) updraft-rear flank gust front.