For average speed, we divide the total distance covered by the total time taken.
After doing that, you will see that Jane has the lowest average speed.
I would say C is the most correct.
In D it depends on what water source you're using. Let's say it is a waterfall, then the source of the water (melting ice or a lake) may disappear in the future.
If you're using underwater "windmills" placed in the ocean, then you would expect it to last a while as the ocean will not disappear in the near future.
I think B but i'm not for sure