Which preposition can indicate a personal opinion?

The preposition "of" in the phrase "of the opinion" is commonly used to express personal beliefs or viewpoints. When someone states they are "of the opinion" about something, they are indicating that they hold a specific belief or perspective regarding a subject. This expression effectively conveys personal judgment or stance, making it a clear indicator of a personal opinion.

The other phrases do not convey the same meaning. "In moderation" refers to a balanced approach to quantity or frequency and is unrelated to personal opinion. "On a regular basis" indicates frequency or routine, and does not express an opinion. "By process" suggests a method or series of steps, which is also unrelated to expressing personal viewpoints. Thus, "of the opinion" stands out as the phrase most directly linked to articulating personal belief.