Answer:
Dr. Tyson<em> (Neil deGrasse Tyson)</em> decided to exclude Pluto from the exhibits of planets because, for him, Pluto was behaving differently from the other planets.<em> It behaved like a comet and was made up of mostly ice.</em> It also crossed orbits which was common for comets but <u>unusual for planets</u>.
Explanation:
The question above is related to the "Astrophysicist Chronicles The Battle Over Pluto." It talks about the reason why Dr. Tyson, the director of the Hayden Planetarium at the American Museum of Natural History, New York City, didn't include the <em>9th planet</em> (Pluto) in his exhibit.
In addition to the answer above, Dr. Tyson also noticed how Pluto was located in the <u>outer solar system</u> in the <em>1990s</em>. This outer solar system is known as the "Kuiper Belt," where you can find other comets and Pluto is considered to be the first object to be identified here.