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