The process by which the ocean floor sinks through a deep ocean trench and back into the mantle is known as A.
convection

B.
continental drift

C.
subduction

D.
conduction

step-by-step explanation:

assume that you have 3 different side lengths.   apply the pythagorean theorem here:   square each of the two shortest sides; call them a and b, so that their squares are a² and b².   also square the longest side, calling the result c².

now, if a² + b² = c² is true, the triangle is a right triangle; otherwise it is not a right triangle.

the answer is 15 to your question