Question

Rivers and mountains are examples of __________ boundaries.

Answer 1

They are not intangible: intangible means that you can't touch it, and you can definitely touch rivers.

They are tangible then: they are physical rather than political - this is the correct answer.

Some rivers and mountains are territory boundaries, but most of them aren't - that's why it's not the correct answer.

Answer 2

Rivers and mountains are examples of territory boundaries. The correct option among all the options that are given in the question is the second option or option "b". There are many countries that have been separated by mountains and rivers from another country. These are demarcations that have been made by the people.