We are to show that the given parametric curve is a circle.
The trajectory of a circle with a radius r will satisfy the following relationship:

(with (x_c,y_c) being the center point)
We are given the x and y in a parametric form which can be further rewritten (using properties of sin/cos):

Squaring and adding both gives:

The last expression shows that the given parametric curve is a circle with the center (0,0) and radius A.
Answer:C
Explanation:
When a constant horizontal force is applied to the box, box started moving in the horizontal direction such that it moves with constant velocity 
Constant velocity implies that net force on the box is zero
i.e. there must be an opposing force which is equal to the applied force and friction force can serve that purpose.
So option c is the correct choice.
Producers, consumers, and decomposers help to move matter and energy through ecosystems.
Hope this helps! :)
Copper, because it has the lowest specific electrical resistance.
specific electrical resistance aka volume resistivity is a fundamental property of a material that quantifies how strongly that material opposes the flow of electric current. A low resistivity indicates a material that readily allows the flow of electric current.
The correct answer is<span> c) Because the moon has no atmosphere, it is not possible for geologic events to occur on the moon.
Atmosphere is related to geological change because of things such as wind and water erosion that over time change the landscape, and there's neither on the moon. It's just a floating rock.</span>