A client reports to the nurse that last night she had difficulty falling sleep. She states she ...

A client reports to the nurse that last night she had difficulty falling sleep. She states she returned
  home from a social evening with friends, during which she consumed several alcoholic drinks.
 
  When unable to fall sleep after half an hour in bed, she brewed herself two cups of herbal tea
  containing valerian. In the morning she awakened with a severe headache and blurred vision. The
  nurse should explain that
  a. valerian should be taken before use of alcohol to avoid unpleasant side effects.
  b. the side effects are those of hangover from excessive alcohol use.
  c. valerian may potentiate the effects of other central nervous system depressants.
  d. herbal teas contain several active ingredients that may produce unpleasant effects.