Warning, this verb may not exist. Conjugation is given as example.
Affirmation
Simple form
I could sniffer you could sniffer he could sniffer we could sniffer you could sniffer they could sniffer
V-ing form
I could be sniffering you could be sniffering he could be sniffering we could be sniffering you could be sniffering they could be sniffering
Perfect
I could have sniffered you could have sniffered he could have sniffered we could have sniffered you could have sniffered they could have sniffered
V-ing perfect
I could have been sniffering you could have been sniffering he could have been sniffering we could have been sniffering you could have been sniffering they could have been sniffering
Negation
Simple form
I could not sniffer you could not sniffer he could not sniffer we could not sniffer you could not sniffer they could not sniffer
V-ing form
I could not be sniffering you could not be sniffering he could not be sniffering we could not be sniffering you could not be sniffering they could not be sniffering
Perfect
I could not have sniffered you could not have sniffered he could not have sniffered we could not have sniffered you could not have sniffered they could not have sniffered
V-ing perfect
I could not have been sniffering you could not have been sniffering he could not have been sniffering we could not have been sniffering you could not have been sniffering they could not have been sniffering
Interrogative form
Simple form
could I sniffer? could you sniffer? could he sniffer? could we sniffer? could you sniffer? could they sniffer?
V-ing form
could I be sniffering? could you be sniffering? could he be sniffering? could we be sniffering? could you be sniffering? could they be sniffering?
Perfect
could I have sniffered? could you have sniffered? could he have sniffered? could we have sniffered? could you have sniffered? could they have sniffered?
V-ing perfect
could I have been sniffering? could you have been sniffering? could he have been sniffering? could we have been sniffering? could you have been sniffering? could they have been sniffering?
Interro-negative form
Simple form
could I not sniffer? could you not sniffer? could he not sniffer? could we not sniffer? could you not sniffer? could they not sniffer?
V-ing form
could I not be sniffering? could you not be sniffering? could he not be sniffering? could we not be sniffering? could you not be sniffering? could they not be sniffering?
Perfect
could I not have sniffered? could you not have sniffered? could he not have sniffered? could we not have sniffered? could you not have sniffered? could they not have sniffered?
V-ing perfect
could I not have been sniffering? could you not have been sniffering? could he not have been sniffering? could we not have been sniffering? could you not have been sniffering? could they not have been sniffering?