I remain unconvinced, and still think (C) is a better answer!
Answer (C) does not say that the nesting boxes are smaller, but just that they provide less space for eggs (because they get overcrowded). In my view, the given statements support this conclusion [that the boxes are smaller than the natural nests] because they seem to link the ducks' failed reproductive efforts to the fact that the boxes become overcrowded. If, by negating this conclusion, the natural nesting sites had just as much, or less, space for eggs, then this reproductive practice would seem to be disadvantageous from the start. Therefore, (C) seems to me to be the right answer.
Answer (D), on the other hand, makes less sense in my view. Why would the ducks' reproductive efforts be more successful when the boxes are hidden? Is the assumption that those nests, though hidden, could still be found by some and thus the practice would become less rare?
Why is it G _>/0 I thought for not both it's a biconditional right? I'm getting biconditional confused with positive conditional-> negative conditional eg G-->/0. Can someone explain the difference of each and when to use them. I saw the biconditional and various conditional videos and I'm still confused.