Jason was recently hired by a security company to design a new password system for a client. He has come up with 4 different designs. Which of the following should Jason choose, assuming he wants to select the one that is the toughest to crack? A) 5 digit password that uses letters only B) 6 digit password that uses a combination of even numbers from 1-9 and vowels C) 8 digit password that uses the numbers 1-9 D)4 digit password that uses a combination of letters and the numbers 1-9