Which of the following is not a disadvantage of using wind power?
a.
turbines are expensive.
b.
birds often fly into fan blades.
c.
energy production decreases at night.
d.
turbines are only effective in specific areas.

The answer would be C. 
the type of energy source that would effect would be solar.

The saharan africa is desert not forest

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.