What would be the best example of bilbo’s approach to the inmost cave / ordeal?

Bilbo approaches Smaug's cave for the first time

Explanation:

onto a large boat, and mark the water level that the boat sinks to. then, take the elephant out and put a bunch of marked weights onto the boat until it reaches the same water level. add up the masses of the weights to get the weight of the elephant.

it is the : d because is true