Venn Diagrams

We are asked to find the set of countries that have either a mountain or a river but do not have a desert. This can be written as the union of the sets of countries with mountains or rivers, excluding those that have deserts.
- represents all countries that have either a mountain or a river.
- represents countries that do not have a desert.
Thus, the required set is the intersection of the set with the complement of (countries that don't have a desert), which gives us .
Therefore, the correct answer is option (c).