If 2/3 of the cards are face-up, then 2/3*12=8 cards are face-up. The remaining 12-8=4 cards are therefore face down.
The right amount to test would be 30.
200 is to many kids and 12 is not enough.
Hope this Helps!!
Narrowing it down it's either a or c because the other 2 choices open downward (negative a).
Graphing the 2 parabolas choice c is narrower.
c
