If you see a word that contains the word part hydra, what do you already know about the word’s meaning? A. It belongs in a story about Greece.
B. It’s related to water.
C. It’s probably a nonsense word.
D. It’s related to outer space.

B.It's related to water.

B. It’s related to water.

Explanation:

I personally would have put A, but that because I'm a geek and I read about these things but the correct answer is B.

The root word of hydra is literally the definition of water (along with Hydro,  & Hydr)

Hope this helps :)

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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.