Read this sentence: "Salivating to food in the mouth is reflexive, so no learning is involved." What is the comma before "so" doing?

1. "Salivating to food in the mouth is reflexive" can stand alone as a complete statement. 2. "No learning is involved" can also stand alone as a complete statement. 3. The word "so" is a linking word showing that the second statement follows from the first. 4. A comma placed before such a linking word is the standard way to join two complete statements, option C. 5. Option A fails because nothing after the comma lists behaviors; there is no series here. 6. Option B fails because no date appears anywhere in the sentence. 7. Option D fails because the comma sits in the middle between two full statements, not after an opening phrase. _Source: OpenStax Psychology 1e (CC BY 4.0), Ch 6 "Learning", section 6.2 Classical Conditioning_