I can sightsee you can sightsee he can sightsee we can sightsee you can sightsee they can sightsee
V-ing form
I can be sightseeing you can be sightseeing he can be sightseeing we can be sightseeing you can be sightseeing they can be sightseeing
Perfect
I can have sightseed you can have sightseed he 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 he can have been sightseeing we can have been sightseeing you can have been sightseeing they can have been sightseeing
Negation
Simple form
I cannot sightsee you cannot sightsee he cannot sightsee we cannot sightsee you cannot sightsee they cannot sightsee
V-ing form
I cannot be sightseeing you cannot be sightseeing he cannot be sightseeing we cannot be sightseeing you cannot be sightseeing they cannot be sightseeing
Perfect
I cannot have sightseed you cannot have sightseed he cannot have sightseed we cannot have sightseed you cannot have sightseed they cannot have sightseed
V-ing perfect
I cannot have been sightseeing you cannot have been sightseeing he cannot have been sightseeing we cannot have been sightseeing you cannot have been sightseeing they cannot have been sightseeing
Interrogative form
Simple form
can I sightsee? can you sightsee? can he sightsee? can we sightsee? can you sightsee? can they sightsee?
V-ing form
can I be sightseeing? can you be sightseeing? can he be sightseeing? can we be sightseeing? can you be sightseeing? can they be sightseeing?
Perfect
can I have sightseed? can you have sightseed? can he 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 he have been sightseeing? can we have been sightseeing? can you have been sightseeing? can they have been sightseeing?
Interro-negative form
Simple form
can I not sightsee? can you not sightsee? can he not sightsee? can we not sightsee? can you not sightsee? can they not sightsee?
V-ing form
can I not be sightseeing? can you not be sightseeing? can he not be sightseeing? can we not be sightseeing? can you not be sightseeing? can they not be sightseeing?
Perfect
can I not have sightseed? can you not have sightseed? can he not have sightseed? can we not have sightseed? can you not have sightseed? can they not have sightseed?
V-ing perfect
can I not have been sightseeing? can you not have been sightseeing? can he not have been sightseeing? can we not have been sightseeing? can you not have been sightseeing? can they not have been sightseeing?