Which of the following is closest in meaning to the phrase "looking up"(Line 1, Para. 2)

A．scientists have discovered the working mechanism of the nose
B．humans detect odors with a large number of receptors responsive to the odorous molecules themselves
C．the receptors integrate various responses to the characteristics of an odor and store them in the brain
D．e-noses operate on principles totally different from those of a real nose

A．the artificial noses are even better than the human noses
B．it has not taken long for the artificial noses to be introduced to the market
C．the attempts of the artificial noses to imitate the olfactory abilities have been largely unsuccessful
D．the artificial noses have their own advantages over the human noses