Of the three languages below, grammatically the simplest one is ______.

A．Because few people like to reverse the cycle of sleep and wakefulness.
B．Because sleep normally coincides with the hours of darkness.
C．Because people are required to work at night in some fields of industry.
D．Because shift work in industry requires people to change their sleeping habits.

A．The structuralism gift of the human brain is that it can invent whole languages.
B．The structuralism gift of the human brain is that it can add tiny structures up to a language.
C．The human vocal system can, like traffic signals, produce sounds a little now and a little then.
D．To separate specific sounds and oppose one to the other is one of the structuralism gifts of the human brain.