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