Click to review the online content. Then answer the question(s) below, using complete sentences. Scroll down to view additional questions. Landforms in Northern Africa What is an erg, and what challenges do they pose for people?

D. a mountain abd are made by volcanos and tectonic plates

If a particular resource is not useful or needed then the price would be considerably low. once that resource is needed the price or value will raise depending on how useful or needed it is especially if the resource is low in quantity, the consumers would pay whatever they have to, to get that material.

Ithink the answer is d.