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