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