Which of the following is a source of carbon dioxide in the atmosphere?
plants
animals
sunlight
factories

Plants, animals, factories.

Explanation:

Plants and animals are living organisms that undergoes aerobic respiration that takes in Oxygen and released carbon dioxide.

Do not be mislead that plants do not give out CO2. During the night, when rate of photosynthesis is slower than rate of respiration, CO2 is released to the atmosphere and acts as a source of CO2.

Animals can only respirate and not photosynthesize. Hence, it is definitely a source of CO2

Factories are sources of CO2 assuming that their operations releases CO2 as by-product which is a very probable event for most factory operations.

Sunlight is a abiotic factor that does not cause CO2 to be released on its own to act as a source of CO2 in the atmosphere.

d i think its   answer d

hormones in blood stream

image: dtc.ucsf.edu

endocrine glands secrete hormones into the blood stream near them; the hormones then travel in our bloodstream until it reaches its destination, called a target cell, in distance parts of the body. in the target tissue, hormones lock onto the target’s plasma membrane, called the receptor site.