Which role of protists, fungi, and bacteria has the most positive effect on maintaining the plant population in an ecosystem? O if they are found in the gut of animals, they can assist in digestion
They are a major food source for animals
They decompose dead materials, returning nutrients to the soil
They produce about 75 percent of the oxygen on Earth

They decompose dead materials, returning nutrients to soil

Explanation:

You could say life on Earth depends on the protists because they supply us with oxygen, are critical organisms in food chains, and recycle important nutrients for other life forms to use.

the correct answer is option b

behavioral response need communication and thus co-ordination at several levels such as interaction among cells, organ system and the entire organism.

behavioral response produces both internal and environmental stimulus.