Answer:
C
Step-by-step explanation:
"Stuff about" is a vague term, and by concrete phrase it is meant that we describe what exactly Mary has to learn.
Consider option A: History of.
Learning the history of a sport will not help one in any way to actually play the game. So, A is incorrect.
Option B: Things about
"things about" again is a vague term and does not describe which things are to be learnt. Throw this option out the window.
Option D: Past and current players.
Thus also won't help one to play the game and know the rules.
Thus, C is the correct choice.