For a hierarchical carry look$-$ahead adder, G$0$ can be written like below. Find the gate delay needed to obtain G$0$ without fan$-$in and with a fan$-$in of $3$ inputs.

G$0=$g$7+$p$7$g$6+$p$7$p$695+$p$7$p$6$p$5$g$4+$p$7$p$6$p$5$p$4$g$3+$p$7$p$6$p$5$p$4$p$3$g$2+$p$7$p$6$p$5$p$4$p$3$p$2$g$1+$p$7$p$6$p $5$p$4$p$3$p$2$p$1$g$0$

Select one:

a$.,$ GO without fan$-$in limitation will require $3$ gate delays

G$0$ with fan$-$in limitation of $3$ will require $5$ gate delays

b$.-$ G$0$ without fan$-$in limitation will require $5$ gate delays

G$0$ with fan$-$in limitation of $3$ will require $3$ gate delays

c$.,$ GO without fan$-$in limitation will require $2$ gate delays

G$0$ with fan$-$in limitation of $3$ will require $4$ gate delays

d$.$

G$0$ without fan$-$in limitation will require $4$ gate delays