I can back you can back she can back we can back you can back they can back
Forma com V-ing
I can be backing you can be backing she can be backing we can be backing you can be backing they can be backing
Perfeito
I can have backed you can have backed she can have backed we can have backed you can have backed they can have backed
Perfeito com V-ing
I can have been backing you can have been backing she can have been backing we can have been backing you can have been backing they can have been backing
Negação
Forma simple
I cannot back you cannot back she cannot back we cannot back you cannot back they cannot back
Forma com V-ing
I cannot be backing you cannot be backing she cannot be backing we cannot be backing you cannot be backing they cannot be backing
Perfeito
I cannot have backed you cannot have backed she cannot have backed we cannot have backed you cannot have backed they cannot have backed
Perfeito com V-ing
I cannot have been backing you cannot have been backing she cannot have been backing we cannot have been backing you cannot have been backing they cannot have been backing
Forma interrogativa
Forma simple
can I back? can you back? can she back? can we back? can you back? can they back?
Forma com V-ing
can I be backing? can you be backing? can she be backing? can we be backing? can you be backing? can they be backing?
Perfeito
can I have backed? can you have backed? can she have backed? can we have backed? can you have backed? can they have backed?
Perfeito com V-ing
can I have been backing? can you have been backing? can she have been backing? can we have been backing? can you have been backing? can they have been backing?
Forma interro-Negação
Forma simple
can I not back? can you not back? can she not back? can we not back? can you not back? can they not back?
Forma com V-ing
can I not be backing? can you not be backing? can she not be backing? can we not be backing? can you not be backing? can they not be backing?
Perfeito
can I not have backed? can you not have backed? can she not have backed? can we not have backed? can you not have backed? can they not have backed?
Perfeito com V-ing
can I not have been backing? can you not have been backing? can she not have been backing? can we not have been backing? can you not have been backing? can they not have been backing?