Answer:
Option B.
Step-by-step explanation:
The given triangle is a right angle triangle.
In a right angle triangle,
[tex]\tan \theta=\dfrac{Perpendicular}{Base}[/tex]
In the given triangle,
[tex]\tan (45^{\circ})=\dfrac{v}{7}[/tex]
[tex]1=\dfrac{v}{7}[/tex]
[tex]7=v[/tex]
Using Pythagoras theorem, we get
[tex]hypotenuse^2=Perpendicular^2+Base^2[/tex]
[tex]u^2=v^2+7^2[/tex]
[tex]u^2=7^2+7^2[/tex]
[tex]u^2=2(7^2)[/tex]
Taking square root on both sides, we get
[tex]u=\sqrt{2(7^2)}[/tex]
[tex]u=7\sqrt{2}[/tex]
Therefore, the correct option is B.