In this, the next-to-last Rocket Spelling level, we throw everything but the kitchen sink at the students! Words like mountains, column, building, and contain are all challenging.
The word separate might be the hardest of all, with many students (and adults) writing it as seperate. Part of the confusion might come from the fact that separate can be either a verb or an adjective, and it often sounds different depending on usage. Consider "The two dogs eat from separate bowls" compared to "I had to separate the two dogs that were chasing each other."