English verb conjugation
COULD INVESTIGATE

Regular verb: investigate - investigated - investigated

Affirmation

Simple form	V-ing form
I could investigate you could investigate he could investigate we could investigate you could investigate they could investigate	I could be investigating you could be investigating he could be investigating we could be investigating you could be investigating they could be investigating
Perfect	V-ing perfect
I could have investigated you could have investigated he could have investigated we could have investigated you could have investigated they could have investigated	I could have been investigating you could have been investigating he could have been investigating we could have been investigating you could have been investigating they could have been investigating

Negation

Simple form	V-ing form
I could not investigate you could not investigate he could not investigate we could not investigate you could not investigate they could not investigate	I could not be investigating you could not be investigating he could not be investigating we could not be investigating you could not be investigating they could not be investigating
Perfect	V-ing perfect
I could not have investigated you could not have investigated he could not have investigated we could not have investigated you could not have investigated they could not have investigated	I could not have been investigating you could not have been investigating he could not have been investigating we could not have been investigating you could not have been investigating they could not have been investigating

Interrogative form

Simple form	V-ing form
could I investigate? could you investigate? could he investigate? could we investigate? could you investigate? could they investigate?	could I be investigating? could you be investigating? could he be investigating? could we be investigating? could you be investigating? could they be investigating?
Perfect	V-ing perfect
could I have investigated? could you have investigated? could he have investigated? could we have investigated? could you have investigated? could they have investigated?	could I have been investigating? could you have been investigating? could he have been investigating? could we have been investigating? could you have been investigating? could they have been investigating?

Interro-negative form

Simple form	V-ing form
could I not investigate? could you not investigate? could he not investigate? could we not investigate? could you not investigate? could they not investigate?	could I not be investigating? could you not be investigating? could he not be investigating? could we not be investigating? could you not be investigating? could they not be investigating?
Perfect	V-ing perfect
could I not have investigated? could you not have investigated? could he not have investigated? could we not have investigated? could you not have investigated? could they not have investigated?	could I not have been investigating? could you not have been investigating? could he not have been investigating? could we not have been investigating? could you not have been investigating? could they not have been investigating?