All these three location provide some kind of barrier be it physical, geographical or due to limited resources and thus lead to speciation
Explanation:
Speciation is a process in which species get isolated from the main group and then become re productively isolated and diverge and hence form new species.
a) A rugged mountain terrain can become a physical barrier there by allowing speciation
b) A large open forest is extremely vast is size and thus species which have traveled to far away distance may not come back and thus get separated there by causing speciation.
c) An island in the Ocean is itself an isolated geographical location . Once a species land on this island, it can never return back to the main group and hence lead to speciation.
