From an aeroplane vertically over a straight horizontal road, the angle of depression of two consecutive kilometre-stones on the opposite sides of the aeroplane are observed to be α and β. The height of the aeroplane above the road is

• A. \(\frac{{{\rm{tan\;\alpha }} + {\rm{tan\;\beta }}}}{{{\rm{tan\;\alpha \;tan\;\beta }}}}\)
• B. \(\frac{{{\rm{tan\;\alpha \;tan\;\beta }}}}{{{\rm{tan\;\alpha }} + {\rm{\;tan\;\beta }}}}\)
• C. \(\frac{{{\rm{cot\;\alpha \;cot\;\beta }}}}{{{\rm{cot\;\alpha }} + {\rm{\;cot\;\beta }}}}\)
• D. \(\frac{{{\rm{cot\;\alpha }} + {\rm{\;cot\;\beta }}}}{{{\rm{cot\;\alpha \;cot\;\beta }}}}\)