For a four-input logic circuit, the truth table must account for all possible combinations of the inputs. Since each input can be either 0 or 1, the total number of combinations is 24=162^4=1624=16. Therefore, the truth table requires 16 entries to cover every possible input state

. This means the truth table will have 16 rows, each representing a unique combination of the four inputs. This is standard for any logic circuit with four binary inputs.