Final answer:
The friend in the left seat takes 4 seconds to move upward, downward, and then back to the initial position.
Therefore, the correct answer is A. 4 seconds.
Step-by-step explanation:
The height of the left seat on the seesaw can be modeled by a sine function. Let's analyze the given data:
t = 0, height = 0 inches
t = 1, height = 24 inches
t = 2, height = 48 inches
t = 3, height = 24 inches
t = 4, height = 0 inches
t = 5, height = 24 inches
t = 6, height = 48 inches
From the data, we can see that the height of the left seat moves upward, downward, and then back to the initial position in a span of 4 seconds. Therefore, the correct answer is A. 4 seconds.