English verb conjugation
COULD RETAIN

Regular verb: retain - retained - retained

Affirmation

Simple form	V-ing form
I could retain you could retain he could retain we could retain you could retain they could retain	I could be retaining you could be retaining he could be retaining we could be retaining you could be retaining they could be retaining
Perfect	V-ing perfect
I could have retained you could have retained he could have retained we could have retained you could have retained they could have retained	I could have been retaining you could have been retaining he could have been retaining we could have been retaining you could have been retaining they could have been retaining

Negation

Simple form	V-ing form
I couldn't retain you couldn't retain he couldn't retain we couldn't retain you couldn't retain they couldn't retain	I couldn't be retaining you couldn't be retaining he couldn't be retaining we couldn't be retaining you couldn't be retaining they couldn't be retaining
Perfect	V-ing perfect
I couldn't have retained you couldn't have retained he couldn't have retained we couldn't have retained you couldn't have retained they couldn't have retained	I couldn't have been retaining you couldn't have been retaining he couldn't have been retaining we couldn't have been retaining you couldn't have been retaining they couldn't have been retaining

Interrogative form

Simple form	V-ing form
could I retain? could you retain? could he retain? could we retain? could you retain? could they retain?	could I be retaining? could you be retaining? could he be retaining? could we be retaining? could you be retaining? could they be retaining?
Perfect	V-ing perfect
could I have retained? could you have retained? could he have retained? could we have retained? could you have retained? could they have retained?	could I have been retaining? could you have been retaining? could he have been retaining? could we have been retaining? could you have been retaining? could they have been retaining?

Interro-negative form

Simple form	V-ing form
couldn't I retain? couldn't you retain? couldn't he retain? couldn't we retain? couldn't you retain? couldn't they retain?	couldn't I be retaining? couldn't you be retaining? couldn't he be retaining? couldn't we be retaining? couldn't you be retaining? couldn't they be retaining?
Perfect	V-ing perfect
couldn't I have retained? couldn't you have retained? couldn't he have retained? couldn't we have retained? couldn't you have retained? couldn't they have retained?	couldn't I have been retaining? couldn't you have been retaining? couldn't he have been retaining? couldn't we have been retaining? couldn't you have been retaining? couldn't they have been retaining?