We use 'can't have Ving' for the past. My question is can we use 'now' with the modal perfect 'can't have Ving' together, or must we use 'by now'?
He can't have done this now. She is not here.
I was going to write 'can't have V3'...Sorry...
He can't have done this now. She is not here. (can we use 'now' or 'by now' in this case?)
"She is not here". I don't understand the place of this sentence in the question.
"He can't have done this" is a good sentence. If you're asking whether you can put 'now' on the end, then no, you can't, for the reason I've given. It's impossible for someone to have done something 'now'. Do you mean 'yet'?
"He can't have done this yet." That makes sense.