I must perceive you must perceive she must perceive we must perceive you must perceive they must perceive
V-ing form
I must be perceiving you must be perceiving she must be perceiving we must be perceiving you must be perceiving they must be perceiving
Perfect
I must have perceived you must have perceived she must have perceived we must have perceived you must have perceived they must have perceived
V-ing perfect
I must have been perceiving you must have been perceiving she must have been perceiving we must have been perceiving you must have been perceiving they must have been perceiving
Negation
Simple form
I mustn't perceive you mustn't perceive she mustn't perceive we mustn't perceive you mustn't perceive they mustn't perceive
V-ing form
I mustn't be perceiving you mustn't be perceiving she mustn't be perceiving we mustn't be perceiving you mustn't be perceiving they mustn't be perceiving
Perfect
I mustn't have perceived you mustn't have perceived she mustn't have perceived we mustn't have perceived you mustn't have perceived they mustn't have perceived
V-ing perfect
I mustn't have been perceiving you mustn't have been perceiving she mustn't have been perceiving we mustn't have been perceiving you mustn't have been perceiving they mustn't have been perceiving
Interrogative form
Simple form
must I perceive? must you perceive? must she perceive? must we perceive? must you perceive? must they perceive?
V-ing form
must I be perceiving? must you be perceiving? must she be perceiving? must we be perceiving? must you be perceiving? must they be perceiving?
Perfect
must I have perceived? must you have perceived? must she have perceived? must we have perceived? must you have perceived? must they have perceived?
V-ing perfect
must I have been perceiving? must you have been perceiving? must she have been perceiving? must we have been perceiving? must you have been perceiving? must they have been perceiving?
Interro-negative form
Simple form
mustn't I perceive? mustn't you perceive? mustn't she perceive? mustn't we perceive? mustn't you perceive? mustn't they perceive?
V-ing form
mustn't I be perceiving? mustn't you be perceiving? mustn't she be perceiving? mustn't we be perceiving? mustn't you be perceiving? mustn't they be perceiving?
Perfect
mustn't I have perceived? mustn't you have perceived? mustn't she have perceived? mustn't we have perceived? mustn't you have perceived? mustn't they have perceived?
V-ing perfect
mustn't I have been perceiving? mustn't you have been perceiving? mustn't she have been perceiving? mustn't we have been perceiving? mustn't you have been perceiving? mustn't they have been perceiving?