The height at which the acceleration due to gravity becomes g/9 (where g = the acceleration due to gravity on the surface of the earth) in terms of R, the radius of the earth, is

- (√2)R
- R/2
- R/√2
- 2R

**Answer**

GM/(9R^{2}) = GM/(R + h)^{2}

3R = R + h

h = 2R

**The correct option is D.**