could sniff
Regular verb: sniff - sniffed- sniffed

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