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