To reach from $(0,0)$ to $(10,10)$ we have to take 20 steps.
Lets assume these 20 steps to be 20 places.
( _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ )
Out of these 20 places to have to choose 10 places for upper steps, the rest of the 10 places have to be for right steps.)
like one example is ( _ u u _ _ u _ _ u _ _uuu_ _u_u_ _ _ _ u), the $‘– ‘$ places should be for right steps.
so, Option $A$ $2nCn$ is the answer.