A person walks along the trail from location C to location D. The person will be walking 1.
downhill then uphill, only
2.
downhill, then uphill, then downhill again
3.
uphill then downhill, only
4.
uphill, then downhill, then uphill again

Ascientist is designing an investigation to study the impact of invasive bird populations on local, native bird populations at backyard bird feeders. what population is most likely to be a control group for the investigation? amount of food number of bird feeders invasive bird populations local backyard birdfeeders without food