Question

multiple choice question
the concentration of co₂ in the atmosphere has increased over the last 150 years primarily due to

increased animal respiration rates
volcanic output
the burning of fossil fuels and deforestation

Explanation:

Animal respiration rates have not significantly increased in the past 150 - year period to cause a major rise in CO₂. Volcanic output is a natural source but not the main contributor to the recent increase. The burning of fossil fuels releases large amounts of CO₂ that was stored for millions of years, and deforestation reduces the number of plants that absorb CO₂ through photosynthesis, leading to a net increase in atmospheric CO₂.

Answer:

the burning of fossil fuels and deforestation