I must nibble you must nibble she must nibble we must nibble you must nibble they must nibble
V-ing form
I must be nibbling you must be nibbling she must be nibbling we must be nibbling you must be nibbling they must be nibbling
Perfect
I must have nibbled you must have nibbled she must have nibbled we must have nibbled you must have nibbled they must have nibbled
V-ing perfect
I must have been nibbling you must have been nibbling she must have been nibbling we must have been nibbling you must have been nibbling they must have been nibbling
Negation
Simple form
I must not nibble you must not nibble she must not nibble we must not nibble you must not nibble they must not nibble
V-ing form
I must not be nibbling you must not be nibbling she must not be nibbling we must not be nibbling you must not be nibbling they must not be nibbling
Perfect
I must not have nibbled you must not have nibbled she must not have nibbled we must not have nibbled you must not have nibbled they must not have nibbled
V-ing perfect
I must not have been nibbling you must not have been nibbling she must not have been nibbling we must not have been nibbling you must not have been nibbling they must not have been nibbling
Interrogative form
Simple form
must I nibble? must you nibble? must she nibble? must we nibble? must you nibble? must they nibble?
V-ing form
must I be nibbling? must you be nibbling? must she be nibbling? must we be nibbling? must you be nibbling? must they be nibbling?
Perfect
must I have nibbled? must you have nibbled? must she have nibbled? must we have nibbled? must you have nibbled? must they have nibbled?
V-ing perfect
must I have been nibbling? must you have been nibbling? must she have been nibbling? must we have been nibbling? must you have been nibbling? must they have been nibbling?
Interro-negative form
Simple form
must I not nibble? must you not nibble? must she not nibble? must we not nibble? must you not nibble? must they not nibble?
V-ing form
must I not be nibbling? must you not be nibbling? must she not be nibbling? must we not be nibbling? must you not be nibbling? must they not be nibbling?
Perfect
must I not have nibbled? must you not have nibbled? must she not have nibbled? must we not have nibbled? must you not have nibbled? must they not have nibbled?
V-ing perfect
must I not have been nibbling? must you not have been nibbling? must she not have been nibbling? must we not have been nibbling? must you not have been nibbling? must they not have been nibbling?