What is the correct way to use the word more in a sentence?
There are a great number of correct ways. Excluding the old noun and verb meanings, “carrot”, “parsnip”, “root”, and “plant”, more can be used as a determiner (“I want more soup”; “We need more bowls”), as an adverb (“He walked more after his bicycle was stolen”; “English is a more beautiful language than French”; “He is more clever than wise”), and as a noun (“The more I wrote, the less sense it made to me”).A good learner’s dictionary or an unabridged general dictionary will help with other examples, especially for the more(!) common uses.
All these sentences use the word "so" correctly except:?
The third sentence is the one that is not correct. In each of the other instances (1, 2, and 4), two separate sentences are set off correctly (either by using a period, the comma and "and", or using a semicolon) -- using a comma without a conjunction (such as "and" or "or") to set off two separate sentences is not acceptable grammar; therefore, the third one is the one that is wrong.