In a right triangle, angle $B$ is an acute angle. Which expression correctly gives $\cos B$ in terms of the side lengths relative to angle $B$?

• A. $\cos B=\frac{\mathrm{opposite}}{\mathrm{hypotenuse}}$
• B. $\cos B=\frac{\mathrm{hypotenuse}}{\mathrm{adjacent}}$
• C. $\cos B=\frac{\mathrm{adjacent}}{\mathrm{hypotenuse}}$
• D. $\cos B=\frac{\mathrm{adjacent}}{\mathrm{opposite}}$

Answer: (C)