Abarrier is

a.

anything that separates things from each other

b.

a connection between two things

c.

anything used to break through something

d.

a large expanse of dry land

Option (A)

Explanation:

A barrier is often defined as an obstacle that does not allow any object or particle to pass through. It leads to the separation of things from one place to another. In terms of geography, a geographical barrier refers to a naturally occurring water body that separates a particular area. Some of the examples of geographic barriers includes mountains, rivers, islands, oceans and glaciers. A geographical barrier can often lead to the occurrence of allopatric speciation.

Thus, the correct answer is option (A).

b.

developed countries have tended to improve the environment, while developing countries have tended to damage it.