A truth table should consider all possible truth values of its simple statements. In this case there are two simple statements, where each one of them can take true or false value, so each of the estatements needs two rows for their individual truth values and, therefore, the compound estatement requires 2x2 = 4 rows for its truth table.
Since, the number of input given to the AND gate in terms of simple statement, the output of the AND gate will give output true if both the statements given to the AND gate will true otherwise it will show output false.
Let's see the truth table for the inputs of two statements
Statement 1 Statement 2 Output
False False False
False True False
True False False
True True True
As we can see the number of rows in the truth table of an AND gate having two input, will have 4 rows.
