The correct answer to this open question is the following.
What is wrong with each design is the following.
First design: the design does not control for distance from the central patch.
Second design: the design does not control for area of the patch.
Third design: there is no difference between the treatments in this design.
Fourth design: the design does not control for edge effects.
We are talking about an important field experiment called Savannah River Corridor Experiment that was the largest corridor experiment up to date. It was designed to study the way corridors function and to learn how corridors affect the habitats and wildlife. It was led by Ellen Damschen from the University of Wisconsin-Madison.