Can someone help me with the following analogy?

colloquy:loquacious
a)somnambulism:ambulatory
b)plateau:flat
c)octahedron:eight
d)toponym:noun

colloquy means conversation

loquacious means talkative

Be sure you understand the definitions of the other words.

What do you think is the best analogy?

I was thinking it could be toponym:noun because a toponym is a place name and a noun is a person, place or thing. Does that make sense?

Think about A.

That was my second guess thank you Ms. Sue.

You're welcome, Carson.

I have one more question. I think the author of this book made a mistake on the next analogy. Take a look and see if you agree.

Platyhelminthes:platypus
a)plateau:platitude
b)worm:marsupial
c)mammal:science
d)crystalline:canine

I think the author mistakenly labeled a platypus as a marsupial. Everything I find says they are not marsupials. Your thoughts?

It is b because a platypus is a platyhhelminthes, and a worm is a marsupial