To expand a 2-bit parallel adder to a 4-bit parallel adder, you must (a) use two 2-bit adders with no interconnections (b) use two 2-bit adders and connect the sum outputs of one to the bit inputs of...

To expand a 2-bit parallel adder to a 4-bit parallel adder, you must
(a) use two 2-bit adders with no interconnections
(b) use two 2-bit adders and connect the sum outputs of one to the bit inputs of the other
(c) use four 2-bit adders with no interconnections
(d) use two 2-bit adders with the carry output of one connected to the carry input of the other