Authentication uses three primary elements:

Something You Know (This would include something only the person attempting to connect would know; an example is Passwords)

Something You Have (This would include something that the person attempting to connect would have; an example is a Cell Phone)

Something You Are (This would include something that the person attempting to connect would be; an example is fingerprints)

which of the three elements you think is the best method for authentication. Include a rationale behind your answer as to why you think this is the most secure method of identifying yourself to a device, service, or application. Discuss why you think one of the other methods is vulnerable and provide an example.