In which of the following adder circuits, the carry look ripple delay is eliminated?

1. Half Adder is a combinational circuit that performs the addition of two bits. sum= A X-OR B, Carry=AB.
2. Full Adder is a combinational circuit that performs the addition of three bits. sum= A X-OR B X-OR Cin, Carry=(A X-OR B)Cin+ AB.
3. Parallel adder is a digital circuit that adds two binary numbers in parallel. 4-bit parallel adder. An n-bit parallel requires n-full adders. the output carry from one package must be connected to the input carry of the one with next higher-order bits. the 4-bit full adder is a typical example of MSI function. also called ripple carry adder.
4. this speeding up the addition process by eliminating the ripple carry delay.