I could achieve you could achieve she could achieve we could achieve you could achieve they could achieve
V-ing form
I could be achieving you could be achieving she could be achieving we could be achieving you could be achieving they could be achieving
Perfect
I could have achieved you could have achieved she could have achieved we could have achieved you could have achieved they could have achieved
V-ing perfect
I could have been achieving you could have been achieving she could have been achieving we could have been achieving you could have been achieving they could have been achieving
Negation
Simple form
I couldn't achieve you couldn't achieve she couldn't achieve we couldn't achieve you couldn't achieve they couldn't achieve
V-ing form
I couldn't be achieving you couldn't be achieving she couldn't be achieving we couldn't be achieving you couldn't be achieving they couldn't be achieving
Perfect
I couldn't have achieved you couldn't have achieved she couldn't have achieved we couldn't have achieved you couldn't have achieved they couldn't have achieved
V-ing perfect
I couldn't have been achieving you couldn't have been achieving she couldn't have been achieving we couldn't have been achieving you couldn't have been achieving they couldn't have been achieving
Interrogative form
Simple form
could I achieve? could you achieve? could she achieve? could we achieve? could you achieve? could they achieve?
V-ing form
could I be achieving? could you be achieving? could she be achieving? could we be achieving? could you be achieving? could they be achieving?
Perfect
could I have achieved? could you have achieved? could she have achieved? could we have achieved? could you have achieved? could they have achieved?
V-ing perfect
could I have been achieving? could you have been achieving? could she have been achieving? could we have been achieving? could you have been achieving? could they have been achieving?
Interro-negative form
Simple form
couldn't I achieve? couldn't you achieve? couldn't she achieve? couldn't we achieve? couldn't you achieve? couldn't they achieve?
V-ing form
couldn't I be achieving? couldn't you be achieving? couldn't she be achieving? couldn't we be achieving? couldn't you be achieving? couldn't they be achieving?
Perfect
couldn't I have achieved? couldn't you have achieved? couldn't she have achieved? couldn't we have achieved? couldn't you have achieved? couldn't they have achieved?
V-ing perfect
couldn't I have been achieving? couldn't you have been achieving? couldn't she have been achieving? couldn't we have been achieving? couldn't you have been achieving? couldn't they have been achieving?