A particle is taken to a height R above the earths surface where R is the radius of the earth. The acceleration due to gravity there is

Given:

$\text{h}=\text{R}$ 

Acceleration due to gravity on the surface of the earth $=\frac{\text{GM}}{{\text{R}}^{\text{2}}}$$=9.8{\text{ms}}^{-2}$

Where G is the universal gravitation constant, M is the mass of the planet, and R is the radius of the planet or the distance of the object from the center of the planet.                      

Acceleration due to gravity at a height (h) from the surface of the earth $=\frac{\text{GM}}{{\left(\text{R}+\text{h}\right)}^{\text{2}}}$

Substituting h=R in the equation,

$=\frac{\text{GM}}{{(\text{R}+\text{R})}^{\text{2}}}=\frac{\text{GM}}{{\left(\text{2R}\right)}^{\text{2}}}=\frac{\text{GM}}{{\text{4R}}^{\text{2}}}=\frac{9.8}{4}=2.45{\text{ms}}^{-2}$

Hence option A will be the correct answer.