Is a system whereby each branch of government exercises some control on the other branches.

As our current atmosphere formed, the concentrations of various atmospheric gases fluctuated. match each gas with the explanation that best describes how its proportion changed during the evolution of the atmosphere.

Danilo has been working for metropolitan taxi for three months. he expected that his job would be to drive around the city, pick up fares, and drop them off at their desired locations, but in his first few days on the job he realized that the job entails much more. he must keep his taxi cab clean and neat, and some days he will be stationed at the shop and go to people's houses to pick them up and bring them to the local airport. within a few months, he has learned that taxi drivers often express frustration with the people they call "civilians"—that is, non–taxi drivers, whose driving skills they complain about incessantly. in his first few months on the job, describes what danilo is undergoing.

Marian recently made the decision to try to re-wallpaper her own kitchen—which was a mistake given her personality! to compound the mistake, she selected a complex wallpaper pattern that included flowers and trees. each time she put one strip of paper on the wall, she became increasingly upset if there was not a perfect match from the pattern of one strip to the next. if one flower was off by as much as one-tenth of an inch, she would tear down the strip, remove the excess paste, and try again with the next strip. over eight hours after she started this job, she has only succeeded at putting up six strips of wallpaper, which covered about 10 percent of the room in which she was working. marian may suffer from personality disorder.