why is 19 necessary assumption instead of sufficient assumption

#help I agree. Ac a and b are just as likely explanation as E

#help

Im soooo confused. We want to explain why birds fly away from vegetation and into window panes instead. AC E says they fly into windows because it reflects vegetation so they think they are flying to vegetation. But why dont they just fly directly to the vegetation? If they chose window panes which also look like vegetation, its says vegetation vs vegetation they chose vegetation? How does this make sense? I chose AC D because predators they know that flying into the vegetation gives them cover, but vegetation does help with noise, vs being indoors can help with the noise.

I got the conditional chain AA→UA→CS. but i dont understand why AC A says that there is no relationship between CS and AA. Why is this wrong? There is a relationship between AA and CS but not a relationship between CS and AA. Because it doesnt go backwards right?

#help (Added by Admin)