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