English verb conjugation
COULD STIFLE

Regular verb: stifle - stifled - stifled

Affirmation

Simple form	V-ing form
I could stifle you could stifle he could stifle we could stifle you could stifle they could stifle	I could be stifling you could be stifling he could be stifling we could be stifling you could be stifling they could be stifling
Perfect	V-ing perfect
I could have stifled you could have stifled he could have stifled we could have stifled you could have stifled they could have stifled	I could have been stifling you could have been stifling he could have been stifling we could have been stifling you could have been stifling they could have been stifling

Negation

Simple form	V-ing form
I couldn't stifle you couldn't stifle he couldn't stifle we couldn't stifle you couldn't stifle they couldn't stifle	I couldn't be stifling you couldn't be stifling he couldn't be stifling we couldn't be stifling you couldn't be stifling they couldn't be stifling
Perfect	V-ing perfect
I couldn't have stifled you couldn't have stifled he couldn't have stifled we couldn't have stifled you couldn't have stifled they couldn't have stifled	I couldn't have been stifling you couldn't have been stifling he couldn't have been stifling we couldn't have been stifling you couldn't have been stifling they couldn't have been stifling

Interrogative form

Simple form	V-ing form
could I stifle? could you stifle? could he stifle? could we stifle? could you stifle? could they stifle?	could I be stifling? could you be stifling? could he be stifling? could we be stifling? could you be stifling? could they be stifling?
Perfect	V-ing perfect
could I have stifled? could you have stifled? could he have stifled? could we have stifled? could you have stifled? could they have stifled?	could I have been stifling? could you have been stifling? could he have been stifling? could we have been stifling? could you have been stifling? could they have been stifling?

Interro-negative form

Simple form	V-ing form
couldn't I stifle? couldn't you stifle? couldn't he stifle? couldn't we stifle? couldn't you stifle? couldn't they stifle?	couldn't I be stifling? couldn't you be stifling? couldn't he be stifling? couldn't we be stifling? couldn't you be stifling? couldn't they be stifling?
Perfect	V-ing perfect
couldn't I have stifled? couldn't you have stifled? couldn't he have stifled? couldn't we have stifled? couldn't you have stifled? couldn't they have stifled?	couldn't I have been stifling? couldn't you have been stifling? couldn't he have been stifling? couldn't we have been stifling? couldn't you have been stifling? couldn't they have been stifling?