English questions about use of , comma I see 2 sentences using , and not using , 1. She is driving now, at the time of speaking. 2. Tom is not reading the book at the time of speaking. what is the difference between using , and not using , the meaning is different, if skip , in the 1 and the meaning is different if i keep , before at the time in 2? what about grammar? 1,2 must be correct sentences, they are from English Grammar In Use by Cambridge university press, Raymond Murphy.