can sniff
Regular verb: sniff - sniffed- sniffed

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

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I can't sniff
you can't sniff
he can't sniff
we can't sniff
you can't sniff
they can't sniff 	I can't be sniffing
you can't be sniffing
he can't be sniffing
we can't be sniffing
you can't be sniffing
they can't be sniffing	I can't have sniffed
you can't have sniffed
he can't have sniffed
we can't have sniffed
you can't have sniffed
they can't have sniffed	I can't have been sniffing
you can't have been sniffing
he can't have been sniffing
we can't have been sniffing
you can't have been sniffing
they can't have been sniffing	

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

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can't I sniff?
can't you sniff?
can't he sniff?
can't we sniff?
can't you sniff?
can't they sniff? 	can't I be sniffing?
can't you be sniffing?
can't he be sniffing?
can't we be sniffing?
can't you be sniffing?
can't they be sniffing? 	can't I have sniffed?
can't you have sniffed?
can't he have sniffed?
can't we have sniffed?
can't you have sniffed?
can't they have sniffed? 	can't I have been sniffing?
can't you have been sniffing?
can't he have been sniffing?
can't we have been sniffing?
can't you have been sniffing?
can't they have been sniffing?