What is the difference between automatic and manual transmission systems?

The distinction between automatic and manual transmission systems primarily centers around gear shifting and control over the vehicle's power delivery.

In an automatic transmission, the system is designed to change gears without the driver's direct intervention, based on factors like vehicle speed and engine load. This allows for smoother and often more efficient operation in a variety of driving conditions. Manual transmission, conversely, requires the driver to manually engage and disengage the gears using a clutch and gear shifter.

Option A correctly highlights that manual transmission systems do not automatically adjust torque; the driver must actively manage gear selection to vary torque. This means that while a manual system provides engagement and control, it lacks the self-adjusting feature of an automatic system, which optimizes torque and gear shifting without the need for driver's input.

Understanding these differences helps in grasping the operational fundamentals of vehicles and the driver-vehicle interaction inherent to each transmission type.