Steps:
(none)
E
WHO
since step 1 has no attributes, it’s just WHO
in our case, yes it is. Because with WH we can get S, and by HOS, we can get E. So we have only one candidate key, that is WHO.
Steps:
in this example it is AD
ABC closures are ABCD, so it is a candidate key BCD closures are ABCD, so it is also a candidate key so in this case we have two candidate keys, they are ABC and BCD.