سوال ۱ کنکور ارشد ریاضی ۱۴۰۵

A place from which information comes is a "source of information" — the natural collocation here. Instagram, as a channel one gets information from, is a poor "source" of medical/health information. The other options do not fit: a "discovery" is something found, a "cause" produces an effect, and "agreement" is a shared understanding — none describes where information originates.