I could tickle you could tickle he could tickle we could tickle you could tickle they could tickle
V-ing form
I could be tickling you could be tickling he could be tickling we could be tickling you could be tickling they could be tickling
Perfect
I could have tickled you could have tickled he could have tickled we could have tickled you could have tickled they could have tickled
V-ing perfect
I could have been tickling you could have been tickling he could have been tickling we could have been tickling you could have been tickling they could have been tickling
Negation
Simple form
I couldn't tickle you couldn't tickle he couldn't tickle we couldn't tickle you couldn't tickle they couldn't tickle
V-ing form
I couldn't be tickling you couldn't be tickling he couldn't be tickling we couldn't be tickling you couldn't be tickling they couldn't be tickling
Perfect
I couldn't have tickled you couldn't have tickled he couldn't have tickled we couldn't have tickled you couldn't have tickled they couldn't have tickled
V-ing perfect
I couldn't have been tickling you couldn't have been tickling he couldn't have been tickling we couldn't have been tickling you couldn't have been tickling they couldn't have been tickling
Interrogative form
Simple form
could I tickle? could you tickle? could he tickle? could we tickle? could you tickle? could they tickle?
V-ing form
could I be tickling? could you be tickling? could he be tickling? could we be tickling? could you be tickling? could they be tickling?
Perfect
could I have tickled? could you have tickled? could he have tickled? could we have tickled? could you have tickled? could they have tickled?
V-ing perfect
could I have been tickling? could you have been tickling? could he have been tickling? could we have been tickling? could you have been tickling? could they have been tickling?
Interro-negative form
Simple form
couldn't I tickle? couldn't you tickle? couldn't he tickle? couldn't we tickle? couldn't you tickle? couldn't they tickle?
V-ing form
couldn't I be tickling? couldn't you be tickling? couldn't he be tickling? couldn't we be tickling? couldn't you be tickling? couldn't they be tickling?
Perfect
couldn't I have tickled? couldn't you have tickled? couldn't he have tickled? couldn't we have tickled? couldn't you have tickled? couldn't they have tickled?
V-ing perfect
couldn't I have been tickling? couldn't you have been tickling? couldn't he have been tickling? couldn't we have been tickling? couldn't you have been tickling? couldn't they have been tickling?