(A)

No. 13

1 Water levels have decreased in many of them.

2 Laws to protect them need to be stricter.

3 Countries sharing them usually have the same usage rights.

4 They often make it difficult to protect borders.

No. 14

1 To suggest a solution to a border problem.

2 To suggest that poor nations need rivers for electricity.

3 To show that dams are often too costly.

4 To show how river usage rights can be complicated.