Which of the following docs the author use as an example of a product whose price has decreased due to changes in technology

A．The effects of climate on the economy.
B．The relation between market prices and technological change.
C．The effect of shifts in supply and demand on market prices.
D．The increasing cost of skilled labor.

A．the fact that these articles are bought by museums
B．the changes in technology that have made such goods cheaper
C．the changes in power supply caused by shrinking oil and mineral reserves
D．the fact that few are being made and so are more expensive to make