Which of the following is correct

$I.$ In a population, birth rate and death rate refer to per capita births and death respectively

$II.$ In nature, we rarely find isolated single individuals of any species

$III.$ The size of population for any species is stable phenomena

$IV.$ Ecological effects of any factors on a population growth are generally reflected in its size/population density

• A

  $I$ and $II$

• B

  $II$ and $III$

• C

  $I, II$ and $III$

• D

  $I, II$ and $IV$