Which summary of this idea best maintains its formal tone?
A. I always used to get mixed up about Pluto being a planet or not
until I saw the solar system model in a museum that got it right.
B. It took a really long time for museums to show that maybe Pluto
isn't a planet, except for this one museum.
C. Scientists had begun to debate privately whether or not Pluto is a
planet, but this was the first time the concept was presented in a
museum for all to see.
D. Museums might not have Pluto in the right spot yet, even though
they're supposed to, because scientists are pretty sure it's not a
planet.