Answer: A.
Explanation: Hope this helps
Circulatory system.....circulates blood (a vital delivery system of oxygen) throughout the whole body when tissues need it the most and with a constant supply.
Answer:The hypothesis that eukaryotic cells evolved from a symbiotic association of prokaryotes—endosymbiosis—is particularly well supported by studies of mitochondria and chloroplasts, which are thought to have evolved from bacteria living in large cells.
Explanation:
a)the number of species on Earth or b)the number of individual organisms on Earth
The answer is sedimentary rock.
