Which planet has the tallest mountain?

since when is Ceres a planet in our solar system and Pluto lost that status some years ago

thats hard to even fathom!! guessed right though!!

Flutterby, they were trying to confuse us

how can this be correctly answered, when we haven't even had any exploration on at least four of these planets Milky Way?

Those planets are not to scale.

Player #2342698, I am definitely not going fathom it,. I am just going to believe it.