The appropriate answer is c. global warming. Global warming is an increase in the global temperature caused by the increased use of fossil fuels. Using fossil fuels since the industrial revolution has pumped extra carbon dioxide in the atmosphere than what would actually enter from natural processes. This extra carbon dioxide is increasing the green house effect and causing the temperature to increase.
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:
Measure only daytime.
Explanation:
It is useless to measure the oxygen production every hour for 24 hours because oxygen is produced during day time due to the presence of photosynthesis process. Oxygen is produced in large amount during photosynthesis, some oxygen is used in respiration while the remaining diffuse out from plant body through stomata. After vanishing sunlight, the photosynthesis process stop and no production of oxygen occur. So only measure oxygen production at daytime as compared to every hour for 24 hours.