Select the group of drug agents that are listed in increasing order of their duration of action. Select one: a. Albuterol (Proventil), Salmeterol/fluticasone (Advair), Tiotropium (Spiriva)
b. Salmeterol/fluticasone (Advair), Albuterol (Proventil), Tiotropium (Spiriva)
c. Albuterol (Proventil), Tiotropium (Spiriva), Salmeterol/fluticasone (Advair)
d. Tiotropium (Spiriva), Albuterol (Proventil), Salmeterol/fluticasone (Advair)