The answer is d. The presence of a cell wall
Primary succession is a process of forming ecosystems in an area that has never been inhabited before. Since living organisms are necessary for forming the soil, which is a foundation of every land ecosystem, at the point before the soil formation or pedogenesis has occurred the ecosystem provides very few habitats.
Involuntary, meaning things in the body such as your heart is all regulated to act unconsciously while also receiving directives from the brain.
Answer:
Active transport often takes place in the internal lining of the small intestine.
Explanation:
