English verb conjugation
COULD SNIFF

Regular verb: sniff - sniffed - sniffed

Affirmation

Simple form	V-ing form
I could sniff you could sniff he could sniff we could sniff you could sniff they could sniff	I could be sniffing you could be sniffing he could be sniffing we could be sniffing you could be sniffing they could be sniffing
Perfect	V-ing perfect
I could have sniffed you could have sniffed he could have sniffed we could have sniffed you could have sniffed they could have sniffed	I could have been sniffing you could have been sniffing he could have been sniffing we could have been sniffing you could have been sniffing they could have been sniffing

Negation

Simple form	V-ing form
I could not sniff you could not sniff he could not sniff we could not sniff you could not sniff they could not sniff	I could not be sniffing you could not be sniffing he could not be sniffing we could not be sniffing you could not be sniffing they could not be sniffing
Perfect	V-ing perfect
I could not have sniffed you could not have sniffed he could not have sniffed we could not have sniffed you could not have sniffed they could not have sniffed	I could not have been sniffing you could not have been sniffing he could not have been sniffing we could not have been sniffing you could not have been sniffing they could not have been sniffing

Interrogative form

Simple form	V-ing form
could I sniff? could you sniff? could he sniff? could we sniff? could you sniff? could they sniff?	could I be sniffing? could you be sniffing? could he be sniffing? could we be sniffing? could you be sniffing? could they be sniffing?
Perfect	V-ing perfect
could I have sniffed? could you have sniffed? could he have sniffed? could we have sniffed? could you have sniffed? could they have sniffed?	could I have been sniffing? could you have been sniffing? could he have been sniffing? could we have been sniffing? could you have been sniffing? could they have been sniffing?

Interro-negative form

Simple form	V-ing form
could I not sniff? could you not sniff? could he not sniff? could we not sniff? could you not sniff? could they not sniff?	could I not be sniffing? could you not be sniffing? could he not be sniffing? could we not be sniffing? could you not be sniffing? could they not be sniffing?
Perfect	V-ing perfect
could I not have sniffed? could you not have sniffed? could he not have sniffed? could we not have sniffed? could you not have sniffed? could they not have sniffed?	could I not have been sniffing? could you not have been sniffing? could he not have been sniffing? could we not have been sniffing? could you not have been sniffing? could they not have been sniffing?