English verb conjugation
CAN ALTER

Regular verb: alter - altered - altered

Affirmation

Simple form	V-ing form
I can alter you can alter he can alter we can alter you can alter they can alter	I can be altering you can be altering he can be altering we can be altering you can be altering they can be altering
Perfect	V-ing perfect
I can have altered you can have altered he can have altered we can have altered you can have altered they can have altered	I can have been altering you can have been altering he can have been altering we can have been altering you can have been altering they can have been altering

Negation

Simple form	V-ing form
I can't alter you can't alter he can't alter we can't alter you can't alter they can't alter	I can't be altering you can't be altering he can't be altering we can't be altering you can't be altering they can't be altering
Perfect	V-ing perfect
I can't have altered you can't have altered he can't have altered we can't have altered you can't have altered they can't have altered	I can't have been altering you can't have been altering he can't have been altering we can't have been altering you can't have been altering they can't have been altering

Interrogative form

Simple form	V-ing form
can I alter? can you alter? can he alter? can we alter? can you alter? can they alter?	can I be altering? can you be altering? can he be altering? can we be altering? can you be altering? can they be altering?
Perfect	V-ing perfect
can I have altered? can you have altered? can he have altered? can we have altered? can you have altered? can they have altered?	can I have been altering? can you have been altering? can he have been altering? can we have been altering? can you have been altering? can they have been altering?

Interro-negative form

Simple form	V-ing form
can't I alter? can't you alter? can't he alter? can't we alter? can't you alter? can't they alter?	can't I be altering? can't you be altering? can't he be altering? can't we be altering? can't you be altering? can't they be altering?
Perfect	V-ing perfect
can't I have altered? can't you have altered? can't he have altered? can't we have altered? can't you have altered? can't they have altered?	can't I have been altering? can't you have been altering? can't he have been altering? can't we have been altering? can't you have been altering? can't they have been altering?