The correct answer is: D. shortage of power
A shortage of power can lead to a shortage of materials, as factories may not be able to operate at full capacity. This can lead to a decrease in the supply of goods and services, which can in turn lead to an increase in prices.
Insufficient advertising may lead to a decrease in demand for a product, but it is not likely to lead to a shortage of materials. Restrictions imposed by quota may also lead to a decrease in demand, but they are not likely to lead to a shortage of materials. Low market demand may lead to a decrease in the production of goods and services, but it is not likely to lead to a shortage of materials.
In conclusion, the key factor that may lead to a shortage of materials is a shortage of power.