The one on the plaque has a triangular grip. Snake B's key has a square grip, so you can exclude B as a possibility.
Following on from Hint 1, next take a look at the keys' teeth.
US Version
It's hard to tell because the keys are facing different directions, but if you compare them closely, the key depicted on the plaque has indentations on two sides--the side at the end and the side facing outward.
Which other keys fit this description?
UK Version
It's hard to tell because the keys are facing different directions, but if you compare them closely, the key depicted on the plaque has indentations on two sides: the side at the end and the side facing outward.
Which other keys fit this description?
Based on the second hint, it can't be A or D, because these have different indentations on the teeth.
This leaves only C and E. What other differences could there be between the keys?
In particular, think about the parts that are almost covered up by the snakes.
Near the base of the grip of each key is a rectangular plate that can face one of two directions.
Snakes C and E both cover up most of the this plate, but if you look closely, you can see which direction each one faces.
Which one faces the same direction as on the plaque?
Solution
Incorrect
Too bad.
Examine each part of the key individually, and compare the options closely.
Correct
Fantasssstic!
It's snake C that has the correct key. The next question is...how on earth are they planning to get it out?