20th
20th Century.
Century is a time period of 100 years (stemming from the Latin cent meaning 100).Centuary is of or pertaining to Centaurs the mythical creatures (half man, half horse).
The twentyfirst century.because if its 2011 it would skip 100 years and it would be the twentyfirst century.
no its the century of the madagascans.
The correct answer is fourth century, in which fourth is spelled out and century has a lowercase c.