Question

Which is a right triangle?

Answer 1

Check each one using the Pytagorean Theorem:
a^2 + b^2 = c^2
If the numbers make that equaiton true, it is a right triangle. If not, it isn't.

Here's how you check the first one:
Is 4^2 + 8^2 = 10^2?
Is 16 + 64 = 100? The answer is no, so the first answer is not a right triangle.

Now check the others the same way.