In Expressions^x, Commas^x, Before and After^x

Thank you. I think there are basically two contexts the expressions or phrases mentioned can be used -- as one to provide extra information and the one that is essential to the overall meaning. As to the former use, if I am not mistaken, I have seen many, many cases where a single comma is...

1) The "has" is required because it shows that it's a present perfect tense, ie. Jones denied using drugs in the past and at present, is still denying it. It's a repetition and continuation of the verb (denied) from the past to the present. If you say "Jones consistently denied", it implies that...