Each time a player has a turn, there are between 1 and 10 possible valid moves that can be made. At the beginning of the game, there are 10 possible valid moves. Near the leaves of the game tree, there are just single valid moves with a minimum value that will win. So, already one can see that, among the choices given in the quiz, 5 is within the range of possibilities.
Indeed, after each move, the maximum number of possible moves decreases by one (since each move crosses out a number), and hence the maximum branching factor will be, on average, 5. |