I can sightsee you can sightsee she can sightsee we can sightsee you can sightsee they can sightsee
V-ing form
I can be sightseeing you can be sightseeing she can be sightseeing we can be sightseeing you can be sightseeing they can be sightseeing
Perfect
I can have sightseed you can have sightseed she can have sightseed we can have sightseed you can have sightseed they can have sightseed
V-ing perfect
I can have been sightseeing you can have been sightseeing she can have been sightseeing we can have been sightseeing you can have been sightseeing they can have been sightseeing
Negation
Simple form
I can't sightsee you can't sightsee she can't sightsee we can't sightsee you can't sightsee they can't sightsee
V-ing form
I can't be sightseeing you can't be sightseeing she can't be sightseeing we can't be sightseeing you can't be sightseeing they can't be sightseeing
Perfect
I can't have sightseed you can't have sightseed she can't have sightseed we can't have sightseed you can't have sightseed they can't have sightseed
V-ing perfect
I can't have been sightseeing you can't have been sightseeing she can't have been sightseeing we can't have been sightseeing you can't have been sightseeing they can't have been sightseeing
Interrogative form
Simple form
can I sightsee? can you sightsee? can she sightsee? can we sightsee? can you sightsee? can they sightsee?
V-ing form
can I be sightseeing? can you be sightseeing? can she be sightseeing? can we be sightseeing? can you be sightseeing? can they be sightseeing?
Perfect
can I have sightseed? can you have sightseed? can she have sightseed? can we have sightseed? can you have sightseed? can they have sightseed?
V-ing perfect
can I have been sightseeing? can you have been sightseeing? can she have been sightseeing? can we have been sightseeing? can you have been sightseeing? can they have been sightseeing?
Interro-negative form
Simple form
can't I sightsee? can't you sightsee? can't she sightsee? can't we sightsee? can't you sightsee? can't they sightsee?
V-ing form
can't I be sightseeing? can't you be sightseeing? can't she be sightseeing? can't we be sightseeing? can't you be sightseeing? can't they be sightseeing?
Perfect
can't I have sightseed? can't you have sightseed? can't she have sightseed? can't we have sightseed? can't you have sightseed? can't they have sightseed?
V-ing perfect
can't I have been sightseeing? can't you have been sightseeing? can't she have been sightseeing? can't we have been sightseeing? can't you have been sightseeing? can't they have been sightseeing?