[A] : All body cells continuously obtain useful material from and dispose of their waste products into the external fluid medium. This is mainly maintained as a constancy and is termed excretion.
[R]: This is achieved by constant disposal or excretion of all waste products and as well as, useless materials from body into external environments.

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

D