A computer engineering student tried to analyze the general situation of adding two bits in an n-bit addition operation. Which of the following best describes the general situation? Select one: a. The 1-bit adder circuit that we learned can be simply concatenated together so that each 1-bit adder will just use two bits from the two operand numbers as inputs. b. All the carry-bits generated by each 1-bit adder will need to be saved somewhere else so that they can be used in another phase of addition operations. c. Each of the 1-bit adder circuits needs to be extended to process three input bits: each bit from the two operand numbers, plus a carry-bit from the addition result of the immediate less significant bits. d. None of the above