I could throb you could throb she could throb we could throb you could throb they could throb
V-ing form
I could be throbbing you could be throbbing she could be throbbing we could be throbbing you could be throbbing they could be throbbing
Perfect
I could have throbbed you could have throbbed she could have throbbed we could have throbbed you could have throbbed they could have throbbed
V-ing perfect
I could have been throbbing you could have been throbbing she could have been throbbing we could have been throbbing you could have been throbbing they could have been throbbing
Negation
Simple form
I could not throb you could not throb she could not throb we could not throb you could not throb they could not throb
V-ing form
I could not be throbbing you could not be throbbing she could not be throbbing we could not be throbbing you could not be throbbing they could not be throbbing
Perfect
I could not have throbbed you could not have throbbed she could not have throbbed we could not have throbbed you could not have throbbed they could not have throbbed
V-ing perfect
I could not have been throbbing you could not have been throbbing she could not have been throbbing we could not have been throbbing you could not have been throbbing they could not have been throbbing
Interrogative form
Simple form
could I throb? could you throb? could she throb? could we throb? could you throb? could they throb?
V-ing form
could I be throbbing? could you be throbbing? could she be throbbing? could we be throbbing? could you be throbbing? could they be throbbing?
Perfect
could I have throbbed? could you have throbbed? could she have throbbed? could we have throbbed? could you have throbbed? could they have throbbed?
V-ing perfect
could I have been throbbing? could you have been throbbing? could she have been throbbing? could we have been throbbing? could you have been throbbing? could they have been throbbing?
Interro-negative form
Simple form
could I not throb? could you not throb? could she not throb? could we not throb? could you not throb? could they not throb?
V-ing form
could I not be throbbing? could you not be throbbing? could she not be throbbing? could we not be throbbing? could you not be throbbing? could they not be throbbing?
Perfect
could I not have throbbed? could you not have throbbed? could she not have throbbed? could we not have throbbed? could you not have throbbed? could they not have throbbed?
V-ing perfect
could I not have been throbbing? could you not have been throbbing? could she not have been throbbing? could we not have been throbbing? could you not have been throbbing? could they not have been throbbing?