English verb conjugation
COULD SIEVE

Regular verb: sieve - sieved - sieved

Affirmation

Simple form	V-ing form
I could sieve you could sieve he could sieve we could sieve you could sieve they could sieve	I could be sieving you could be sieving he could be sieving we could be sieving you could be sieving they could be sieving
Perfect	V-ing perfect
I could have sieved you could have sieved he could have sieved we could have sieved you could have sieved they could have sieved	I could have been sieving you could have been sieving he could have been sieving we could have been sieving you could have been sieving they could have been sieving

Negation

Simple form	V-ing form
I couldn't sieve you couldn't sieve he couldn't sieve we couldn't sieve you couldn't sieve they couldn't sieve	I couldn't be sieving you couldn't be sieving he couldn't be sieving we couldn't be sieving you couldn't be sieving they couldn't be sieving
Perfect	V-ing perfect
I couldn't have sieved you couldn't have sieved he couldn't have sieved we couldn't have sieved you couldn't have sieved they couldn't have sieved	I couldn't have been sieving you couldn't have been sieving he couldn't have been sieving we couldn't have been sieving you couldn't have been sieving they couldn't have been sieving

Interrogative form

Simple form	V-ing form
could I sieve? could you sieve? could he sieve? could we sieve? could you sieve? could they sieve?	could I be sieving? could you be sieving? could he be sieving? could we be sieving? could you be sieving? could they be sieving?
Perfect	V-ing perfect
could I have sieved? could you have sieved? could he have sieved? could we have sieved? could you have sieved? could they have sieved?	could I have been sieving? could you have been sieving? could he have been sieving? could we have been sieving? could you have been sieving? could they have been sieving?

Interro-negative form

Simple form	V-ing form
couldn't I sieve? couldn't you sieve? couldn't he sieve? couldn't we sieve? couldn't you sieve? couldn't they sieve?	couldn't I be sieving? couldn't you be sieving? couldn't he be sieving? couldn't we be sieving? couldn't you be sieving? couldn't they be sieving?
Perfect	V-ing perfect
couldn't I have sieved? couldn't you have sieved? couldn't he have sieved? couldn't we have sieved? couldn't you have sieved? couldn't they have sieved?	couldn't I have been sieving? couldn't you have been sieving? couldn't he have been sieving? couldn't we have been sieving? couldn't you have been sieving? couldn't they have been sieving?