A circulatory system is very essential in mammals but not in smaller organisms like Amoeba because?

A. Amoeba lives in freshwater
B. Diffusion is sufficient to transport materials in Amoeba
C. Amoeba lacks blood containing haemoglobin
D. Amoeba exhibits anaerobic respiration

Correct Answer:

Option B – Diffusion is sufficient to transport materials in Amoeba