4b
In the impersonal passive sentence, the subject follows the verb, and it has the structure ‘It + passive verb (+ that) + subject + verb’. The impersonal passive always starts with ‘it’ followed by the passive form of verb of the main clause. In the personal passive sentence ‘the stunt’ becomes the subject of the sentence, and it has the form ‘subject + passive verb + to-infinitive of the verb of the subordinate clause (in the appropriate tense).