Question

The blades of a windmill turn on an axis that is 35 feet above the ground. The blades are 10 feet long and complete two rotations every minute. Which of the following equations can be used to model h, the height in feet of the end of one blade, as a function of time, t, in seconds? Assume that the blade is pointing to the right, parallel to the ground at t = 0 seconds, and that the windmill turns counterclockwise at a constant rate.

Answer 1

No equation on your list can be used to model 'h', because
you didn't provide a list. That leaves me wondering just what
"the following" means, and it leaves me to create an equation
out of thin air.

So there's no way I can help you pick the right choice from
the list of choices. But if you see anything there that looks
like this:

h = 35 + 10 cos( π t / 30 )

then go ahead and pick that one.

Answer 2

It could be C. If the blade spends twice in a minute, it would be 30 seconds. 30=2pi/B=pi/15.