@zrg121 Hello. This is the way I reasoned through this problem. With ac A, you do not have to assume that the bees ARE part of the insects that don't depend on perceiving an object's color. The very fact that they COULD be, strengthens the conclusion. If insects like bees don't depend on perceiving an object's color, it is probably that bees don't either (since they are like them). This probably in itself means that its less likely that the bees are developing their vision in response to the flower colors. On the other hand, ac C requires at least 2 assumptions for it to be a strengthener. The way you put it, you would have to assume that 1. the number of flowers correlates to the number of different colors and that 2. effectiveness is a factor in explaining why one thing or another adapts (which is not necessarily a reasonable assumption, because a lot of things can influence how things adapt). These assumptions are both needed for ac C to even be potentially considered a strengthener. Compare that to A where the very truth of the statement (the possibility that the bees are one of these insects) weakens the alternative hypothesis and, by that very fact, strengthens our hypothesis.

Though they initially seemed unnecessary, they were actually very helpful for thinking about how to parse through difficult stimuli/passages