I could strain you could strain he could strain we could strain you could strain they could strain
V-ing form
I could be straining you could be straining he could be straining we could be straining you could be straining they could be straining
Perfect
I could have strained you could have strained he could have strained we could have strained you could have strained they could have strained
V-ing perfect
I could have been straining you could have been straining he could have been straining we could have been straining you could have been straining they could have been straining
Negation
Simple form
I could not strain you could not strain he could not strain we could not strain you could not strain they could not strain
V-ing form
I could not be straining you could not be straining he could not be straining we could not be straining you could not be straining they could not be straining
Perfect
I could not have strained you could not have strained he could not have strained we could not have strained you could not have strained they could not have strained
V-ing perfect
I could not have been straining you could not have been straining he could not have been straining we could not have been straining you could not have been straining they could not have been straining
Interrogative form
Simple form
could I strain? could you strain? could he strain? could we strain? could you strain? could they strain?
V-ing form
could I be straining? could you be straining? could he be straining? could we be straining? could you be straining? could they be straining?
Perfect
could I have strained? could you have strained? could he have strained? could we have strained? could you have strained? could they have strained?
V-ing perfect
could I have been straining? could you have been straining? could he have been straining? could we have been straining? could you have been straining? could they have been straining?
Interro-negative form
Simple form
could I not strain? could you not strain? could he not strain? could we not strain? could you not strain? could they not strain?
V-ing form
could I not be straining? could you not be straining? could he not be straining? could we not be straining? could you not be straining? could they not be straining?
Perfect
could I not have strained? could you not have strained? could he not have strained? could we not have strained? could you not have strained? could they not have strained?
V-ing perfect
could I not have been straining? could you not have been straining? could he not have been straining? could we not have been straining? could you not have been straining? could they not have been straining?