Given below are two statements; one is labelled as Assertion A and the other is labelled as Reason
R. Assertion A; When a body is projected at an angle $45^{\circ}$, it's range is maximum.
Reason R: For maximum range, the value of $\sin 2 \theta$ should be equal to one.
In the light of the above statements, choose the correct answer from the options given below :