English verb conjugation
COULD MASTER

Regular verb: master - mastered - mastered

Affirmation

Simple form	V-ing form
I could master you could master she could master we could master you could master they could master	I could be mastering you could be mastering she could be mastering we could be mastering you could be mastering they could be mastering
Perfect	V-ing perfect
I could have mastered you could have mastered she could have mastered we could have mastered you could have mastered they could have mastered	I could have been mastering you could have been mastering she could have been mastering we could have been mastering you could have been mastering they could have been mastering

Negation

Simple form	V-ing form
I couldn't master you couldn't master she couldn't master we couldn't master you couldn't master they couldn't master	I couldn't be mastering you couldn't be mastering she couldn't be mastering we couldn't be mastering you couldn't be mastering they couldn't be mastering
Perfect	V-ing perfect
I couldn't have mastered you couldn't have mastered she couldn't have mastered we couldn't have mastered you couldn't have mastered they couldn't have mastered	I couldn't have been mastering you couldn't have been mastering she couldn't have been mastering we couldn't have been mastering you couldn't have been mastering they couldn't have been mastering

Interrogative form

Simple form	V-ing form
could I master? could you master? could she master? could we master? could you master? could they master?	could I be mastering? could you be mastering? could she be mastering? could we be mastering? could you be mastering? could they be mastering?
Perfect	V-ing perfect
could I have mastered? could you have mastered? could she have mastered? could we have mastered? could you have mastered? could they have mastered?	could I have been mastering? could you have been mastering? could she have been mastering? could we have been mastering? could you have been mastering? could they have been mastering?

Interro-negative form

Simple form	V-ing form
couldn't I master? couldn't you master? couldn't she master? couldn't we master? couldn't you master? couldn't they master?	couldn't I be mastering? couldn't you be mastering? couldn't she be mastering? couldn't we be mastering? couldn't you be mastering? couldn't they be mastering?
Perfect	V-ing perfect
couldn't I have mastered? couldn't you have mastered? couldn't she have mastered? couldn't we have mastered? couldn't you have mastered? couldn't they have mastered?	couldn't I have been mastering? couldn't you have been mastering? couldn't she have been mastering? couldn't we have been mastering? couldn't you have been mastering? couldn't they have been mastering?