The length of the shadow of a tower standing on level ground is found to 2x meter longer when the sun’s elevation is 30° than when it was 45 °. The height of the tower in meters is

• A. $\left( {\sqrt 3+ 1} \right)\,x$$
• B. $\left( {\sqrt 3- 1} \right)\,x$$
• C. $2\sqrt 3 \,x$$
• D. $3\sqrt 2 \,x$$