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 can't weld you can't weld he can't weld we can't weld you can't weld they can't weld
V-ing form
I can't be welding you can't be welding he can't be welding we can't be welding you can't be welding they can't be welding
Perfect
I can't have welded you can't have welded he can't have welded we can't have welded you can't have welded they can't have welded
V-ing perfect
I can't have been welding you can't have been welding he can't have been welding we can't have been welding you can't have been welding they can't 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't I weld? can't you weld? can't he weld? can't we weld? can't you weld? can't they weld?
V-ing form
can't I be welding? can't you be welding? can't he be welding? can't we be welding? can't you be welding? can't they be welding?
Perfect
can't I have welded? can't you have welded? can't he have welded? can't we have welded? can't you have welded? can't they have welded?
V-ing perfect
can't I have been welding? can't you have been welding? can't he have been welding? can't we have been welding? can't you have been welding? can't they have been welding?