I can weld you can weld he can weld we can weld you can weld they can weld
V-ing form
I can be welding you can be welding he can be welding we can be welding you can be welding they can be welding
Perfect
I can have welded you can have welded he can have welded we can have welded you can have welded they can have welded
V-ing perfect
I can have been welding you can have been welding he can have been welding we can have been welding you can have been welding they can have been welding
Negation
Simple form
I cannot weld you cannot weld he cannot weld we cannot weld you cannot weld they cannot weld
V-ing form
I cannot be welding you cannot be welding he cannot be welding we cannot be welding you cannot be welding they cannot be welding
Perfect
I cannot have welded you cannot have welded he cannot have welded we cannot have welded you cannot have welded they cannot have welded
V-ing perfect
I cannot have been welding you cannot have been welding he cannot have been welding we cannot have been welding you cannot have been welding they cannot have been welding
Interrogative form
Simple form
can I weld? can you weld? can he weld? can we weld? can you weld? can they weld?
V-ing form
can I be welding? can you be welding? can he be welding? can we be welding? can you be welding? can they be welding?
Perfect
can I have welded? can you have welded? can he have welded? can we have welded? can you have welded? can they have welded?
V-ing perfect
can I have been welding? can you have been welding? can he have been welding? can we have been welding? can you have been welding? can they have been welding?
Interro-negative form
Simple form
can I not weld? can you not weld? can he not weld? can we not weld? can you not weld? can they not weld?
V-ing form
can I not be welding? can you not be welding? can he not be welding? can we not be welding? can you not be welding? can they not be welding?
Perfect
can I not have welded? can you not have welded? can he not have welded? can we not have welded? can you not have welded? can they not have welded?
V-ing perfect
can I not have been welding? can you not have been welding? can he not have been welding? can we not have been welding? can you not have been welding? can they not have been welding?