Which of the following is one way to assess whether or not a learning game is effective?

a) being able to win the game
b) doing a quiz before and after the game to see what you have learned
c) making it difficult to win the game
d) simulating winning

One of the ways to assess whether or not a learning game is effective is B. doing a quiz before and after the game to see what you have learned.
The point of a learning game is of course to learn something, so giving your students a quiz before and after the game will show how much they have progressed. 

B
The purpose of the game is to teach; therefore, testing knowledge before and after the game is a good way to check its effectiveness.