What is the minimum requirement for RAM for Windows $10?$

Question $12$ options:

a$)$

$1$ GB for $32$bit, $2$G for $64$bit

b$)$

$4$ GB for $32$bit, $8$G for $64$bit

c$)$

$8$ GB for $32$bit, $16$G for $64$bit

d$)$

$16$ GB for $32$bit, $32$G for $64$b