It's set by the supply and demand of the good. The less of it available and higher demand for it, the more it costs. The more of it available and lower demand for it, the cheaper it is.
A. B. C. E are the answers
One widely accepted notion — outside of the medical profession, that is — had German spies deliberately seeding Boston Harbor with influenza-sprouting germs.
It would be the term "c. inflation" that refers to an economic situation where the large amount of money in circulation creates continuous pressure to raise prices, since the value of the money actually decreases.