I can alert you can alert she can alert we can alert you can alert they can alert
V-ing form
I can be alerting you can be alerting she can be alerting we can be alerting you can be alerting they can be alerting
Perfect
I can have alerted you can have alerted she can have alerted we can have alerted you can have alerted they can have alerted
V-ing perfect
I can have been alerting you can have been alerting she can have been alerting we can have been alerting you can have been alerting they can have been alerting
Negation
Simple form
I can't alert you can't alert she can't alert we can't alert you can't alert they can't alert
V-ing form
I can't be alerting you can't be alerting she can't be alerting we can't be alerting you can't be alerting they can't be alerting
Perfect
I can't have alerted you can't have alerted she can't have alerted we can't have alerted you can't have alerted they can't have alerted
V-ing perfect
I can't have been alerting you can't have been alerting she can't have been alerting we can't have been alerting you can't have been alerting they can't have been alerting
Interrogative form
Simple form
can I alert? can you alert? can she alert? can we alert? can you alert? can they alert?
V-ing form
can I be alerting? can you be alerting? can she be alerting? can we be alerting? can you be alerting? can they be alerting?
Perfect
can I have alerted? can you have alerted? can she have alerted? can we have alerted? can you have alerted? can they have alerted?
V-ing perfect
can I have been alerting? can you have been alerting? can she have been alerting? can we have been alerting? can you have been alerting? can they have been alerting?
Interro-negative form
Simple form
can't I alert? can't you alert? can't she alert? can't we alert? can't you alert? can't they alert?
V-ing form
can't I be alerting? can't you be alerting? can't she be alerting? can't we be alerting? can't you be alerting? can't they be alerting?
Perfect
can't I have alerted? can't you have alerted? can't she have alerted? can't we have alerted? can't you have alerted? can't they have alerted?
V-ing perfect
can't I have been alerting? can't you have been alerting? can't she have been alerting? can't we have been alerting? can't you have been alerting? can't they have been alerting?