4 is CORRECT. (169)10 = (A9)16, where A is the hexadecimal representation of the decimal number '10', obtained by dividing 169 by 16 two times and recording the remainders: 169/16 = 10 with r = 9; 10/16 = 0 with r = 10 (which is an A). Stop here because 0 was reached. Read the r numbers backwards to get A9.