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