Answer
The kingdom Monera is no longer considered a valid taxon due to having members from two different domains. Domains are a higher level of classification than kingdoms. Monera used to be used to classify prokaryotes, but since they have been found out to span over two domains (Archaea and Bacteria), it is now obsolete.
Work Step by Step
Look over Chapter 26.6 and pay attention to the old and current systems of taxonomy that have been used. Note the changes.
