could participate
Verbo regular: participate - participated- participated

Afirmação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I could participate
you could participate
he could participate
we could participate
you could participate
they could participate 	I could be participating
you could be participating
he could be participating
we could be participating
you could be participating
they could be participating	I could have participated
you could have participated
he could have participated
we could have participated
you could have participated
they could have participated	I could have been participating
you could have been participating
he could have been participating
we could have been participating
you could have been participating
they could have been participating	

Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I couldn't participate
you couldn't participate
he couldn't participate
we couldn't participate
you couldn't participate
they couldn't participate 	I couldn't be participating
you couldn't be participating
he couldn't be participating
we couldn't be participating
you couldn't be participating
they couldn't be participating	I couldn't have participated
you couldn't have participated
he couldn't have participated
we couldn't have participated
you couldn't have participated
they couldn't have participated	I couldn't have been participating
you couldn't have been participating
he couldn't have been participating
we couldn't have been participating
you couldn't have been participating
they couldn't have been participating	

Forma interrogativa 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
could I participate?
could you participate?
could he participate?
could we participate?
could you participate?
could they participate? 	could I be participating?
could you be participating?
could he be participating?
could we be participating?
could you be participating?
could they be participating? 	could I have participated?
could you have participated?
could he have participated?
could we have participated?
could you have participated?
could they have participated? 	could I have been participating?
could you have been participating?
could he have been participating?
could we have been participating?
could you have been participating?
could they have been participating? 	

Forma interro-Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
couldn't I participate?
couldn't you participate?
couldn't he participate?
couldn't we participate?
couldn't you participate?
couldn't they participate? 	couldn't I be participating?
couldn't you be participating?
couldn't he be participating?
couldn't we be participating?
couldn't you be participating?
couldn't they be participating? 	couldn't I have participated?
couldn't you have participated?
couldn't he have participated?
couldn't we have participated?
couldn't you have participated?
couldn't they have participated? 	couldn't I have been participating?
couldn't you have been participating?
couldn't he have been participating?
couldn't we have been participating?
couldn't you have been participating?
couldn't they have been participating?