Final answer:
The rate at which the skydiver descended is found by dividing the total distance fallen (400 feet) by the total time taken (5 seconds), resulting in a descent rate of 80 feet per second.
Step-by-step explanation:
The question seeks to find the rate of descent of a skydiver who falls 400 feet in 5 seconds. To determine this rate, we need to divide the total distance fallen by the total time taken. The rate of descent (velocity) can be calculated using the formula: velocity = distance / time.
In this case, the skydiver fell 400 feet in 5 seconds. Therefore, the rate at which the skydiver descended is:
Rate of descent = 400 feet / 5 seconds = 80 feet per second.
Thus, the correct answer is D. 80 feet per second.