Hello,
I'm not sure I understand the second rule that "any two birds that are both of the same sex and of the same kind as each other cannot be caged together." Does it mean as long as the two birds are in different genders AND in different kind, they can be caged together, i.e., besides Q, R, any one of them can do?? Also, why is the answer D instead of E? I feel both answers are the same. R/S are of the same kind in the same gender, it doesn't really matter which one is chosen??