The reason why people announce that "things are not what they were in my young days" is that their ______ is not the same as before.

A．Through food.
B．Through air.
C．Through insects.
D．Through body fluids.

A．How historical events affected an art movement.
B．How artists can influence economic conditions.
C．Why a certain art movement failed to become popular.
D．How valuable paintings were lost during wartime.