When Deficits in the Sense of Smell Have Been Studied

When deficits in the sense of smell have been studied, it has been found that smokers are:

A) twice as effective as nonsmokers at detecting danger by smelling a fire's smoke.
B) likely to detect odours in the same manner as nonsmokers after quitting for one year.
C) nearly twice as likely as nonsmokers to have trouble detecting common odours.
D) equally likely as nonsmokers to have trouble detecting common odours.