I can fast you can fast he can fast we can fast you can fast they can fast
V-ing form
I can be fasting you can be fasting he can be fasting we can be fasting you can be fasting they can be fasting
Perfect
I can have fasted you can have fasted he can have fasted we can have fasted you can have fasted they can have fasted
V-ing perfect
I can have been fasting you can have been fasting he can have been fasting we can have been fasting you can have been fasting they can have been fasting
Negation
Simple form
I can't fast you can't fast he can't fast we can't fast you can't fast they can't fast
V-ing form
I can't be fasting you can't be fasting he can't be fasting we can't be fasting you can't be fasting they can't be fasting
Perfect
I can't have fasted you can't have fasted he can't have fasted we can't have fasted you can't have fasted they can't have fasted
V-ing perfect
I can't have been fasting you can't have been fasting he can't have been fasting we can't have been fasting you can't have been fasting they can't have been fasting
Interrogative form
Simple form
can I fast? can you fast? can he fast? can we fast? can you fast? can they fast?
V-ing form
can I be fasting? can you be fasting? can he be fasting? can we be fasting? can you be fasting? can they be fasting?
Perfect
can I have fasted? can you have fasted? can he have fasted? can we have fasted? can you have fasted? can they have fasted?
V-ing perfect
can I have been fasting? can you have been fasting? can he have been fasting? can we have been fasting? can you have been fasting? can they have been fasting?
Interro-negative form
Simple form
can't I fast? can't you fast? can't he fast? can't we fast? can't you fast? can't they fast?
V-ing form
can't I be fasting? can't you be fasting? can't he be fasting? can't we be fasting? can't you be fasting? can't they be fasting?
Perfect
can't I have fasted? can't you have fasted? can't he have fasted? can't we have fasted? can't you have fasted? can't they have fasted?
V-ing perfect
can't I have been fasting? can't you have been fasting? can't he have been fasting? can't we have been fasting? can't you have been fasting? can't they have been fasting?