Final answer:
The component that transfers power from the transmission to the rear axle in a rear-wheel-drive truck is the driveshaft. It is a crucial part for vehicle propulsion and should not be confused with other components like CV axles, rear control arms, or transaxles that serve different functions in a vehicle's drive system.
Step-by-step explanation:
In a rear-wheel-drive truck, the component that transfers power from the transmission to the rear axle is known as the driveshaft. The driveshaft is a long, cylindrical shaft that transmits the rotational force from the transmission, where the engine's power is modified, to the drive wheels at the rear axle which moves the vehicle. This process is vital for the propulsion of the truck. Other options listed, such as CV axle, rear control arms, and transaxle, perform different functions. For instance, a CV axle is commonly used in vehicles with front-wheel drive or all-wheel drive, rear control arms are part of the suspension system, and a transaxle combines the functions of transmission and driveline components and is typically found in front-wheel-drive vehicles.