English verb conjugation
COULD SING

Irregular verb: sing - sang - sung

Affirmation

Simple form	V-ing form
I could sing you could sing she could sing we could sing you could sing they could sing	I could be singing you could be singing she could be singing we could be singing you could be singing they could be singing
Perfect	V-ing perfect
I could have sung you could have sung she could have sung we could have sung you could have sung they could have sung	I could have been singing you could have been singing she could have been singing we could have been singing you could have been singing they could have been singing

Negation

Simple form	V-ing form
I couldn't sing you couldn't sing she couldn't sing we couldn't sing you couldn't sing they couldn't sing	I couldn't be singing you couldn't be singing she couldn't be singing we couldn't be singing you couldn't be singing they couldn't be singing
Perfect	V-ing perfect
I couldn't have sung you couldn't have sung she couldn't have sung we couldn't have sung you couldn't have sung they couldn't have sung	I couldn't have been singing you couldn't have been singing she couldn't have been singing we couldn't have been singing you couldn't have been singing they couldn't have been singing

Interrogative form

Simple form	V-ing form
could I sing? could you sing? could she sing? could we sing? could you sing? could they sing?	could I be singing? could you be singing? could she be singing? could we be singing? could you be singing? could they be singing?
Perfect	V-ing perfect
could I have sung? could you have sung? could she have sung? could we have sung? could you have sung? could they have sung?	could I have been singing? could you have been singing? could she have been singing? could we have been singing? could you have been singing? could they have been singing?

Interro-negative form

Simple form	V-ing form
couldn't I sing? couldn't you sing? couldn't she sing? couldn't we sing? couldn't you sing? couldn't they sing?	couldn't I be singing? couldn't you be singing? couldn't she be singing? couldn't we be singing? couldn't you be singing? couldn't they be singing?
Perfect	V-ing perfect
couldn't I have sung? couldn't you have sung? couldn't she have sung? couldn't we have sung? couldn't you have sung? couldn't they have sung?	couldn't I have been singing? couldn't you have been singing? couldn't she have been singing? couldn't we have been singing? couldn't you have been singing? couldn't they have been singing?