Which of the following was once a volcano under the ocean?
a. sea stack
b. cave
c. ocean trench
d. seamount

The correct answer is (d.) seamount. A seamount is a mountain rising from an ocean floor, however, it does not reach the water surface, thus, it is not considered as an island or whatsoever. It was indeed once a volcano under the ocean.

In a right-angled triangle: 1- the hypotenuse is the longest side2- we can apply pythagorean rule which states that: (hypotenuse)^2 = (side1)^2 + (side2)^2for the given triangle,longest side is 15 cm  side1 = 9 cmside2 is 12 cm  to check whether the triangle is right-angled or not,compare (15)^2 to the summation of (9)^2 and (12)^in other words, compare 225 to the summation of 81 and 144if they are both equal, then the triangle is right-angles, otherwise, it is not.you haven't provided the diagram showing her work, so i cannot tell the choice. however, apply my explanation to the question you have.

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