In advanced English morphosyntax and voice diathesis, active-to-passive voice transformations frequently involve complex structures such as causative constructions, sensory verbs taking bare infinitives, prepositional verbs, and complex modal auxiliaries. Consider the following four advanced propositions regarding active and passive voice conversion: I. When converting an active sentence featuring a causative verb followed by a bare infinitive (e.g., 'The harsh economic climate made the multinational corporation reduce its workforce'), standard English passive syntax requires the bare infinitive to obligatorily convert into a full to-infinitive in the passive counterpart (e.g., 'The multinational corporation was made to reduce its workforce by the harsh economic climate'), recovering the historical marker 'to' that remains unexpressed in the active voice. II. When an active clause contains a ditransitive verb taking both an indirect and a direct object (e.g., 'The committee granted the principal investigator an extension'), promoting the direct object (the theme) to the subject position while retaining the indirect object (the recipient) in its original noun phrase slot without a preposition is grammatically fully well-formed in standard English (e.g., 'An extension was granted the principal investigator by the committee'). III. In active sentences governed by verbs of sensory perception or cognition taking bare infinitives (e.g., 'The eyewitness observed the suspect conceal the stolen artifact'), the passive transformation mandates that the bare infinitive transforms into a full to-infinitive (e.g., 'The suspect was observed to conceal the stolen artifact by the eyewitness'), thereby satisfying strict syntactic requirements. IV. When an active clause contains a prepositional verb where the preposition forms a fixed lexical unit with the verb (e.g., 'The board of directors laughed at the absurd proposal'), standard English passive conversion requires the preposition to be detached from the lexical verb and placed exclusively at the absolute beginning of the sentence as a fronted marker rather than remaining stranded adjacent to the verb (e.g., 'At was laughed the absurd proposal by the board of directors'). Identify the option that correctly evaluates the grammatical, syntactic, and semantic validity of propositions I, II, III, and IV according to standard English grammar and English passive voice principles.