A patient who wants to quit smoking has a prescription for varenicline [Chantix], which will be used with a nicotine patch. The patient asks the nurse why the varenicline is necessary. Which statement by the nurse is correct?a. "It helps patients experiencing withdrawal to sleep better."b. "It helps reduce anxiety and other withdrawal symptoms."c. "It will help reduce the likelihood of addiction to the patch."d. "The drug blocks nicotine's access to 'pleasure' receptors."