Which of the following statements is/are correct?
$(i)$ The shape of the cells may vary with the function they perform.
$(ii)$ Human $RBC$ is about $7.0 \; \mu m$ in diameter.
$(iii)$ Cytoplasm is the main area of cellular activities.
$(iv)$ Various chemical reactions occur in cytoplasm to keep the cell in the living state.

• A
  $(i), (ii), (iii)$ and $(iv)$
• B
  Only $(i)$ and $(ii)$
• C
  Only $(iv)$
• D
  None of the above