The angle of elevation of the top of a tower, vertically erected in the middle of a paddy field, from two points on a horizontal line through the foot of the tower are given to be α and β (α>β). The height of the tower is h unit. A possible distance (in the same unit) between the points is

• A. h(cotβ-cotα)cos(α+β)
• B. h(cotα - cotβ)
• C. h(tanβ - tanα)tanα tanβ
• D. h(cotα+cotβ)