The angle of elevation of the top of a tower at a point on the ground 50 m away from the foot of the tower is 45°. Then the height of the tower (in metres) is

• A. $50\sqrt 3 $$
• B. $50$$
• C. $\frac{{50}}{{\sqrt 2 }}$$
• D. $\frac{{50}}{{\sqrt 3 }}$$