The greenhouse effect is the trapping of a stars warmth in the lower atmosphere of a planet by gasses in the air trapping the energy. This is similar to what actual greenhouses do, where they trap the warmth and humidity of the air inside it so plants can flourish. Farm animals produce a huge amount of the greenhouse gasses required for our planet to trap the suns warmth.
C. Agar provides a solid surface for bacterial growth.
Agar is a substance obtained from red algae which when added to a culture media, provides a solid surface for the growth of bacteria. When the agar is not added then the culture media remains as the broth and when the agar is added then the broth gets solidified.
Agar is added 1.5-2% in the broth to get solidified. The growth of the bacteria depends on the amount of agar added. Agar is used for the growth of bacteria because it has gel like properties which holds the nutrients evenly and the bacteria can use it accordingly.
It is described as relatively non specific
It's a mutualism relationship because both species can benefit from each other.
I believe the answer is D) Eukarya