During a typical upshift, the synchronizer must perform which action?

During a typical upshift, the synchronizer's primary role is to match the rotating speeds of the gears involved in the shift. This means that the synchronizer needs to facilitate the slowing down of the clutch disc, main drive gear, cluster gear, and the speed gears to a point where they can engage smoothly without clashing.

When a driver initiates an upshift, they are generally moving from a lower gear to a higher gear. The engine speed (RPM) should be reduced relative to the input speed of the transmitting components. The series of actions taken by the synchronizer ensures that the new gear can mesh with the ongoing rotation of the driveshaft at a compatible speed, allowing for seamless engagement and preventing gear damage or wear from clash or grinding.

The other options focus incorrectly on the direct behaviors of the clutch or engine RPMs, which do not capture the critical function of the synchronizer during the shifting process. It is the synchronizer's task specifically to manage and synchronize speed to allow for a proper gear change.