I could quibble you could quibble he could quibble we could quibble you could quibble they could quibble
V-ing form
I could be quibbling you could be quibbling he could be quibbling we could be quibbling you could be quibbling they could be quibbling
Perfect
I could have quibbled you could have quibbled he 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 he could have been quibbling we could have been quibbling you could have been quibbling they could have been quibbling
Negation
Simple form
I could not quibble you could not quibble he could not quibble we could not quibble you could not quibble they could not quibble
V-ing form
I could not be quibbling you could not be quibbling he could not be quibbling we could not be quibbling you could not be quibbling they could not be quibbling
Perfect
I could not have quibbled you could not have quibbled he could not have quibbled we could not have quibbled you could not have quibbled they could not have quibbled
V-ing perfect
I could not have been quibbling you could not have been quibbling he could not have been quibbling we could not have been quibbling you could not have been quibbling they could not have been quibbling
Interrogative form
Simple form
could I quibble? could you quibble? could he quibble? could we quibble? could you quibble? could they quibble?
V-ing form
could I be quibbling? could you be quibbling? could he be quibbling? could we be quibbling? could you be quibbling? could they be quibbling?
Perfect
could I have quibbled? could you have quibbled? could he 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 he have been quibbling? could we have been quibbling? could you have been quibbling? could they have been quibbling?
Interro-negative form
Simple form
could I not quibble? could you not quibble? could he not quibble? could we not quibble? could you not quibble? could they not quibble?
V-ing form
could I not be quibbling? could you not be quibbling? could he not be quibbling? could we not be quibbling? could you not be quibbling? could they not be quibbling?
Perfect
could I not have quibbled? could you not have quibbled? could he not have quibbled? could we not have quibbled? could you not have quibbled? could they not have quibbled?
V-ing perfect
could I not have been quibbling? could you not have been quibbling? could he not have been quibbling? could we not have been quibbling? could you not have been quibbling? could they not have been quibbling?