Of the 59 matings in the experimental groups, how many were between like-adapted flies (flies adapted to the same medium?

According to another source, its 42. 

This experiment has involved testing like-adapted flies on how they are adapted to the environment, in this case medium. Experiments help out testing on the effects of one medium from the other and how organisms such as these like-adapted flies would react and make a significant difference from those unlike-adapted flies.  

Ithink it’s c or b for the answer.