Final answer:
The drive that mitigates shock loading during startup is the fluid drive, which uses a fluid coupling to transmit power gently and reduce mechanical shock.
Step-by-step explanation:
The drive that relieves the driven fan of shock loading during startup is the: A) Fluid drive. A fluid drive, also known as a hydraulic drive, uses a fluid coupling to transmit power from the motor to the driven equipment, allowing for controlled acceleration and reducing the risk of mechanical shock. This type of drive is beneficial in applications where the load is variable or if gentle startup is necessary to prevent damage. Options B), C), and D) can have various purposes in different systems but are not principally designed to relieve shock loading during startup.