I can grade you can grade she can grade we can grade you can grade they can grade
V-ing form
I can be grading you can be grading she can be grading we can be grading you can be grading they can be grading
Perfect
I can have graded you can have graded she can have graded we can have graded you can have graded they can have graded
V-ing perfect
I can have been grading you can have been grading she can have been grading we can have been grading you can have been grading they can have been grading
Negation
Simple form
I can't grade you can't grade she can't grade we can't grade you can't grade they can't grade
V-ing form
I can't be grading you can't be grading she can't be grading we can't be grading you can't be grading they can't be grading
Perfect
I can't have graded you can't have graded she can't have graded we can't have graded you can't have graded they can't have graded
V-ing perfect
I can't have been grading you can't have been grading she can't have been grading we can't have been grading you can't have been grading they can't have been grading
Interrogative form
Simple form
can I grade? can you grade? can she grade? can we grade? can you grade? can they grade?
V-ing form
can I be grading? can you be grading? can she be grading? can we be grading? can you be grading? can they be grading?
Perfect
can I have graded? can you have graded? can she have graded? can we have graded? can you have graded? can they have graded?
V-ing perfect
can I have been grading? can you have been grading? can she have been grading? can we have been grading? can you have been grading? can they have been grading?
Interro-negative form
Simple form
can't I grade? can't you grade? can't she grade? can't we grade? can't you grade? can't they grade?
V-ing form
can't I be grading? can't you be grading? can't she be grading? can't we be grading? can't you be grading? can't they be grading?
Perfect
can't I have graded? can't you have graded? can't she have graded? can't we have graded? can't you have graded? can't they have graded?
V-ing perfect
can't I have been grading? can't you have been grading? can't she have been grading? can't we have been grading? can't you have been grading? can't they have been grading?