To double the covering range of a TV transimitter tower, its height should be made

Options

A. 2 tims
B. 4 times
C. `sqrt(2)` times
D. 8 times

Explanation

As covering ranges, `d=sqrt(2h R)`, where symbols have their usual meaning.
As `d=sqrt(h)` or `h=d^(2)` so `(h')/(h)=((2d)^(2))/(d^(2))=4`
or `h'=4h` therefore, to double the covering range d, h must be made 4 times.