Which of the following would be considered a"hard", high contrast, impermeable border(vs. a "soft", low contrast, permeable one?

Which of the following would be considered a "hard", high contrast, impermeable border (vs. a "soft", low contrast, permeable one?)

Note: There are THREE correct answers, and all correct answers must be selected in order to earn the point for this question.

A.forests leading into shrublands on a mountainside

B.railroad tracks

C.a tall barbed-wire fence

D.beach sloping into sand dunes

E.a highway