Maria places a rock in a graduated cylinder containing some water

B. 26 mL

Explanation:

The volume of the water in the graduated cylinder is displaced when a rock is placed inside.

To find the volume of both combined simply look at the volume of the water.

You have to look at the very bottom of the curve of the water, this curve is called a meniscus, if we look at the bottom of the blue curve we can see that it is around 25-26 mL of water.

Therefore that is the answer.

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