English verb conjugation
COULD SUBSTITUTE

Regular verb: substitute - substituted - substituted

Affirmation

Simple form	V-ing form
I could substitute you could substitute she could substitute we could substitute you could substitute they could substitute	I could be substituting you could be substituting she could be substituting we could be substituting you could be substituting they could be substituting
Perfect	V-ing perfect
I could have substituted you could have substituted she could have substituted we could have substituted you could have substituted they could have substituted	I could have been substituting you could have been substituting she could have been substituting we could have been substituting you could have been substituting they could have been substituting

Negation

Simple form	V-ing form
I couldn't substitute you couldn't substitute she couldn't substitute we couldn't substitute you couldn't substitute they couldn't substitute	I couldn't be substituting you couldn't be substituting she couldn't be substituting we couldn't be substituting you couldn't be substituting they couldn't be substituting
Perfect	V-ing perfect
I couldn't have substituted you couldn't have substituted she couldn't have substituted we couldn't have substituted you couldn't have substituted they couldn't have substituted	I couldn't have been substituting you couldn't have been substituting she couldn't have been substituting we couldn't have been substituting you couldn't have been substituting they couldn't have been substituting

Interrogative form

Simple form	V-ing form
could I substitute? could you substitute? could she substitute? could we substitute? could you substitute? could they substitute?	could I be substituting? could you be substituting? could she be substituting? could we be substituting? could you be substituting? could they be substituting?
Perfect	V-ing perfect
could I have substituted? could you have substituted? could she have substituted? could we have substituted? could you have substituted? could they have substituted?	could I have been substituting? could you have been substituting? could she have been substituting? could we have been substituting? could you have been substituting? could they have been substituting?

Interro-negative form

Simple form	V-ing form
couldn't I substitute? couldn't you substitute? couldn't she substitute? couldn't we substitute? couldn't you substitute? couldn't they substitute?	couldn't I be substituting? couldn't you be substituting? couldn't she be substituting? couldn't we be substituting? couldn't you be substituting? couldn't they be substituting?
Perfect	V-ing perfect
couldn't I have substituted? couldn't you have substituted? couldn't she have substituted? couldn't we have substituted? couldn't you have substituted? couldn't they have substituted?	couldn't I have been substituting? couldn't you have been substituting? couldn't she have been substituting? couldn't we have been substituting? couldn't you have been substituting? couldn't they have been substituting?