Answer:
See the answer below
Explanation:
Person X is feeling a burning sensation in several muscles<u> because of the accumulation of lactic acid due to inadequate oxygen in their system.</u> When oxygen becomes inadequate during exercises, anaerobic respiration takes place to augment the oxygen shortage and this leads to the production of lactic acid which accumulates up in the muscles and gives a burning sensation.

Person Y does not feel any burning sensation in their muscles <u>because oxygen is adequate in their system and they do not need to respire anaerobically.</u> <em>Person X exercise regime must have been more rigorous than that of person Y.</em>
Answer:
C.) Competition within species leads to some organisms being more fit
Explanation:
They might get the resource but they won't always win.
Answer:Without leaves green plants could not live.
Explanation:because from leaves a plant take breath or do respiration. In leaves of plants there are small pores or stomata from where they breathe. So if we can't breathe we can't live.so,Without leaves green plants could not live.
5. Because of rain and oxygen, if a set of tools is left outdoors in the rain for a long time, it will rust.
6. Yes, I believe it is possible for any of the earth materials scenes to be affected by both mechanical and Chemical weathering, but I am more positive about #5.