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