Your are the filtering system for your blood.
a. urethra
b. sweat glands
c. kidneys
d. hormones

Option (A)

Explanation: Plant has the ability to produce food by absorbing carbon dioxide, and releasing oxygen, this process is known as the photosynthesis process. The CO₂ present in the atmosphere is produced by the humans and organisms during exhalation.

The more CO₂ a plant receives, the more it can undergo photosynthesis, and there is reduction in the level of CO₂.

Thus, according to the given condition, if we add plants to the flask, then the CO₂ content will reduce and will be provided with oxygen in return.

Thus, the correct answer is option (A).