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