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