1. Make sentences in the passive voice of modal verbs as follows: He may be criticized by his father. He may have been criticized by his father; This playground should be built in my school.

2. Define the passive voice with modal verbs: it is used to explain the emotions or attitudes reflected by the passive actions of someone or something.

Modal verbs are words that express the speaker's views or subjective assumptions about a certain behavior or state. They have certain meanings, but they can't be used as predicates independently, and they can only form predicates together with verb prototypes.

Modal verbs are used before action verbs. Although the number of modal verbs is small, they are widely used. Modal verbs mainly include the following words: can, can, must, need, should, dare, should and will.

Passive voice is a special form of verb, which is used to explain the relationship between subject and predicate verb, indicating that subject is the receiver of action. Generally speaking, only transitive verbs that need action objects have passive voice. The passive voice consists of "the auxiliary verb be+ and the past participle of the transitive verb", and its temporal change only changes the form of be, but the past participle remains unchanged.