Select the mismatched pair in the following and correct it.
$(a)$ Biomagnification — Accumulation of chemicals at the successive trophic levels of a food chain
$(b)$ Ecosystem — Biotic components of environment
$(c)$ Aquarium — $A$ man-made ecosystem
$(d)$ Parasites — Organisms which obtain food from other living organisms

• A
  Biomagnification — Accumulation of chemicals at the successive trophic levels of a food chain
• B
  Ecosystem — Biotic components of environment
• C
  Aquarium — $A$ man-made ecosystem
• D
  Parasites — Organisms which obtain food from other living organisms