A combinational circuit's outputs depend on

a$.$ current values of the inputs only.

b$.$current values of the inputs as well as the present state.

c$.$current as well as past values of the inputs

d$.$

both $b$ and $c.$

Which group below is a functionally complete set of gates?

a$.$AND, OR

b$.$ NOT, AND

c$.$NOR

d$.$NOT, OR