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