A Stratified Sample Is Taken from a Population of Size $N=2000$

Multiple Choice

A stratified sample is taken from a population of size $N=2000$ which consists of two strata of $N_{1}=800$ , $N_{2}=1200, n_{1}=20, n_{2}=40, \sigma_{1}=3, \sigma_{2}=5$ . Then the method of allocation is

A) proportional.
B) optimum.
C) neither proportional nor optimum.
D) both proportional and optimum.