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