I could calve you could calve she could calve we could calve you could calve they could calve
V-ing form
I could be calving you could be calving she could be calving we could be calving you could be calving they could be calving
Perfect
I could have calved you could have calved she could have calved we could have calved you could have calved they could have calved
V-ing perfect
I could have been calving you could have been calving she could have been calving we could have been calving you could have been calving they could have been calving
Negation
Simple form
I couldn't calve you couldn't calve she couldn't calve we couldn't calve you couldn't calve they couldn't calve
V-ing form
I couldn't be calving you couldn't be calving she couldn't be calving we couldn't be calving you couldn't be calving they couldn't be calving
Perfect
I couldn't have calved you couldn't have calved she couldn't have calved we couldn't have calved you couldn't have calved they couldn't have calved
V-ing perfect
I couldn't have been calving you couldn't have been calving she couldn't have been calving we couldn't have been calving you couldn't have been calving they couldn't have been calving
Interrogative form
Simple form
could I calve? could you calve? could she calve? could we calve? could you calve? could they calve?
V-ing form
could I be calving? could you be calving? could she be calving? could we be calving? could you be calving? could they be calving?
Perfect
could I have calved? could you have calved? could she have calved? could we have calved? could you have calved? could they have calved?
V-ing perfect
could I have been calving? could you have been calving? could she have been calving? could we have been calving? could you have been calving? could they have been calving?
Interro-negative form
Simple form
couldn't I calve? couldn't you calve? couldn't she calve? couldn't we calve? couldn't you calve? couldn't they calve?
V-ing form
couldn't I be calving? couldn't you be calving? couldn't she be calving? couldn't we be calving? couldn't you be calving? couldn't they be calving?
Perfect
couldn't I have calved? couldn't you have calved? couldn't she have calved? couldn't we have calved? couldn't you have calved? couldn't they have calved?
V-ing perfect
couldn't I have been calving? couldn't you have been calving? couldn't she have been calving? couldn't we have been calving? couldn't you have been calving? couldn't they have been calving?