could preinvestigate
Regular verb: preinvestigate - preinvestigated- preinvestigated

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could preinvestigate
you could preinvestigate
he could preinvestigate
we could preinvestigate
you could preinvestigate
they could preinvestigate 	I could be preinvestigating
you could be preinvestigating
he could be preinvestigating
we could be preinvestigating
you could be preinvestigating
they could be preinvestigating	I could have preinvestigated
you could have preinvestigated
he could have preinvestigated
we could have preinvestigated
you could have preinvestigated
they could have preinvestigated	I could have been preinvestigating
you could have been preinvestigating
he could have been preinvestigating
we could have been preinvestigating
you could have been preinvestigating
they could have been preinvestigating	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not preinvestigate
you could not preinvestigate
he could not preinvestigate
we could not preinvestigate
you could not preinvestigate
they could not preinvestigate 	I could not be preinvestigating
you could not be preinvestigating
he could not be preinvestigating
we could not be preinvestigating
you could not be preinvestigating
they could not be preinvestigating	I could not have preinvestigated
you could not have preinvestigated
he could not have preinvestigated
we could not have preinvestigated
you could not have preinvestigated
they could not have preinvestigated	I could not have been preinvestigating
you could not have been preinvestigating
he could not have been preinvestigating
we could not have been preinvestigating
you could not have been preinvestigating
they could not have been preinvestigating	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I preinvestigate?
could you preinvestigate?
could he preinvestigate?
could we preinvestigate?
could you preinvestigate?
could they preinvestigate? 	could I be preinvestigating?
could you be preinvestigating?
could he be preinvestigating?
could we be preinvestigating?
could you be preinvestigating?
could they be preinvestigating? 	could I have preinvestigated?
could you have preinvestigated?
could he have preinvestigated?
could we have preinvestigated?
could you have preinvestigated?
could they have preinvestigated? 	could I have been preinvestigating?
could you have been preinvestigating?
could he have been preinvestigating?
could we have been preinvestigating?
could you have been preinvestigating?
could they have been preinvestigating? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not preinvestigate?
could you not preinvestigate?
could he not preinvestigate?
could we not preinvestigate?
could you not preinvestigate?
could they not preinvestigate? 	could I not be preinvestigating?
could you not be preinvestigating?
could he not be preinvestigating?
could we not be preinvestigating?
could you not be preinvestigating?
could they not be preinvestigating? 	could I not have preinvestigated?
could you not have preinvestigated?
could he not have preinvestigated?
could we not have preinvestigated?
could you not have preinvestigated?
could they not have preinvestigated? 	could I not have been preinvestigating?
could you not have been preinvestigating?
could he not have been preinvestigating?
could we not have been preinvestigating?
could you not have been preinvestigating?
could they not have been preinvestigating?