Correct Response: C. Weight reduction is a paramount goal in rocket design. It takes a massive amount of energy to escape the earth's gravitational pull, and any reduction in weight significantly reduces the amount of fuel required for the rocket to reach orbit. Therefore, once the lower stages have accomplished their tasks, they are jettisoned for weight savings. Without such a multistage system, empty fuel storage containers would weigh down the rocket for no reason. Once empty, the lower stages only serve to reduce efficiency (A) until they are jettisoned. Reuse of jettisoned stages (B) reduces cost associated with multistaging, but is not the primary reasoning for multistaging. Once a stage separates from the rocket, it can no longer provide additional thrust (D).
