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