Final answer:
The synonym for chronic course is 4) long-term course, indicating a lasting or recurrent illness over an extended period.
Step-by-step explanation:
The synonym for chronic course is long-term course. Unlike an acute course, which is short-term and where pathologic changes occur over a relatively short time, a chronic disease lasts for months or years. The term chronic indicates ongoing or recurrent illness without complete resolution of symptoms, as opposed to acute diseases like influenza, which have a rapid onset and a relatively short duration.