The number of fill and half$-$address required to add $16-$bit number is:

a$.4$ half$-$adders, $12$ full$-$adders

b$.16$ half$-$adders, $0$ full$-$adders

c$.1$ half$-$adder, $15$ full$-$adders

d$.8$ half$-$adders, $8$ full$-$adders