English verb conjugation
COULD FILTER

Regular verb: filter - filtered - filtered

Affirmation

Simple form	V-ing form
I could filter you could filter he could filter we could filter you could filter they could filter	I could be filtering you could be filtering he could be filtering we could be filtering you could be filtering they could be filtering
Perfect	V-ing perfect
I could have filtered you could have filtered he could have filtered we could have filtered you could have filtered they could have filtered	I could have been filtering you could have been filtering he could have been filtering we could have been filtering you could have been filtering they could have been filtering

Negation

Simple form	V-ing form
I couldn't filter you couldn't filter he couldn't filter we couldn't filter you couldn't filter they couldn't filter	I couldn't be filtering you couldn't be filtering he couldn't be filtering we couldn't be filtering you couldn't be filtering they couldn't be filtering
Perfect	V-ing perfect
I couldn't have filtered you couldn't have filtered he couldn't have filtered we couldn't have filtered you couldn't have filtered they couldn't have filtered	I couldn't have been filtering you couldn't have been filtering he couldn't have been filtering we couldn't have been filtering you couldn't have been filtering they couldn't have been filtering

Interrogative form

Simple form	V-ing form
could I filter? could you filter? could he filter? could we filter? could you filter? could they filter?	could I be filtering? could you be filtering? could he be filtering? could we be filtering? could you be filtering? could they be filtering?
Perfect	V-ing perfect
could I have filtered? could you have filtered? could he have filtered? could we have filtered? could you have filtered? could they have filtered?	could I have been filtering? could you have been filtering? could he have been filtering? could we have been filtering? could you have been filtering? could they have been filtering?

Interro-negative form

Simple form	V-ing form
couldn't I filter? couldn't you filter? couldn't he filter? couldn't we filter? couldn't you filter? couldn't they filter?	couldn't I be filtering? couldn't you be filtering? couldn't he be filtering? couldn't we be filtering? couldn't you be filtering? couldn't they be filtering?
Perfect	V-ing perfect
couldn't I have filtered? couldn't you have filtered? couldn't he have filtered? couldn't we have filtered? couldn't you have filtered? couldn't they have filtered?	couldn't I have been filtering? couldn't you have been filtering? couldn't he have been filtering? couldn't we have been filtering? couldn't you have been filtering? couldn't they have been filtering?