Answer:
<h2>C. maintenance </h2>
Explanation:
I personally believe one key disadvantages is the cost of maintaining the equipment unlike the gym where you have to subscribe for the month or the year and forget about anything, owning the gym equipment comes with the extra cost and responsibilities of maintenance to the owners.
Earlier in the text this question is provided for, you should be able to find the passage, "The currently accepted theory attributes ice ages to small changes in Earth's orbit, known as Milankovitch cycles. These cycles describe how Earth's orbit gradually changes shape from more circular to more elliptical and back again. This happens roughly every 100,000 years. The orbital changes take Earth nearer and further from the Sun, which would affect the amount of energy reaching Earth."
Answer: Small changes in Earth's orbit
That's the Cosmic Microwave Background (CMB). (D)
It doesn't "provide evidence for the ... Theory". The Big Bang theory is the best explanation (so far) for the CMB and a lot of other observations.
Evidence isn't used to prove theories. Theories are attempts to explain evidence.