Given, m=5, n=4, 5x4 board
To calculate the number of unique paths, we need to consider the number of horizontal [right] and vertical [down] moves.
For the given board, to travel from top-left to bottom-right according to the given constraints we need 4 rights/horizontal moves and 3 downs/vertical moves.
Therefore, totally we need to make 7 moves.
Therefore, number of unique paths = 7! / (4! x 3! ) = 35
Answer is option C) 35