One of these things is not like the others
Please go to the Question #12 post if you haven't had a chance work on this one yet, since the text below contains the solution.
A femtosecond is one millionth of one billionth of a second. A fortnight is 14 days. And a millennium is one thousand years. The fourth item on the list, parsec, is not a measurement of time, but rather of distance. So, parsec does not belong. It is not like the others.