I could dilute you could dilute he could dilute we could dilute you could dilute they could dilute
V-ing form
I could be diluting you could be diluting he could be diluting we could be diluting you could be diluting they could be diluting
Perfect
I could have diluted you could have diluted he could have diluted we could have diluted you could have diluted they could have diluted
V-ing perfect
I could have been diluting you could have been diluting he could have been diluting we could have been diluting you could have been diluting they could have been diluting
Negation
Simple form
I couldn't dilute you couldn't dilute he couldn't dilute we couldn't dilute you couldn't dilute they couldn't dilute
V-ing form
I couldn't be diluting you couldn't be diluting he couldn't be diluting we couldn't be diluting you couldn't be diluting they couldn't be diluting
Perfect
I couldn't have diluted you couldn't have diluted he couldn't have diluted we couldn't have diluted you couldn't have diluted they couldn't have diluted
V-ing perfect
I couldn't have been diluting you couldn't have been diluting he couldn't have been diluting we couldn't have been diluting you couldn't have been diluting they couldn't have been diluting
Interrogative form
Simple form
could I dilute? could you dilute? could he dilute? could we dilute? could you dilute? could they dilute?
V-ing form
could I be diluting? could you be diluting? could he be diluting? could we be diluting? could you be diluting? could they be diluting?
Perfect
could I have diluted? could you have diluted? could he have diluted? could we have diluted? could you have diluted? could they have diluted?
V-ing perfect
could I have been diluting? could you have been diluting? could he have been diluting? could we have been diluting? could you have been diluting? could they have been diluting?
Interro-negative form
Simple form
couldn't I dilute? couldn't you dilute? couldn't he dilute? couldn't we dilute? couldn't you dilute? couldn't they dilute?
V-ing form
couldn't I be diluting? couldn't you be diluting? couldn't he be diluting? couldn't we be diluting? couldn't you be diluting? couldn't they be diluting?
Perfect
couldn't I have diluted? couldn't you have diluted? couldn't he have diluted? couldn't we have diluted? couldn't you have diluted? couldn't they have diluted?
V-ing perfect
couldn't I have been diluting? couldn't you have been diluting? couldn't he have been diluting? couldn't we have been diluting? couldn't you have been diluting? couldn't they have been diluting?