Which of these is NOT one of the basic styles of pressure plates?

The correct choice is the Marcel style of pressure plates, which is not a recognized basic style. In the context of manual transmissions, pressure plates serve an essential function in the clutch system, ensuring proper engagement and disengagement of the engine's power to the transmission.

The diaphragm and push/pull types are widely recognized styles of pressure plates. The diaphragm pressure plate utilizes a single diaphragm spring to apply force uniformly across the clutch disc, enhancing performance and providing faster engagement. Push-type systems apply pressure through a mechanism that pushes the clutch disc against the flywheel when engaged, while pull-type systems do the opposite, pulling the disc away from the flywheel.

The Marcel design, however, does not fit within these distinct categories and is not a standard pressure plate type. Instead, it may refer to a specific design feature or a manufacturer’s branding but does not pertain to the fundamental classifications typically found in clutch systems. This is why it is correctly identified as not being one of the basic styles of pressure plates.