In advanced English morphosyntax, aspectual distinction and tense interaction govern the precise temporal framing of complex events across independent and dependent clauses. Consider the following four advanced propositions regarding tenses and their correct usage: I. When reporting a past habitual action or a continuous background state that was interrupted by a sudden discrete event, the simultaneous background activity is correctly framed using the past continuous tense, while the interrupting event is cast in the simple past tense (e.g., 'While the committee was deliberating the budget proposal, the director entered the boardroom'). II. The present perfect continuous tense is grammatically appropriate for describing an ongoing action that commenced at a definite point in the past and continues into the present moment, but it is strictly ungrammatical when combined with stative verbs or verbs of perception that lack duration (e.g., *'He has been knowing the truth for years'*). III. In narrative discourse, the historical present is utilized to recount past events vividly as if they are unfolding in real time; however, once the narrative framework is established in the present tense, it is syntactically permissible and stylistically seamless to intermix simple past and present perfect forms arbitrarily without causing temporal discord. IV. The future perfect continuous tense combines future time projection with duration up to a specified point in the future, correctly requiring the auxiliary structure 'will have been' followed by the present participle (e.g., 'By next December, she will have been leading the research initiative for a decade'). 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 tense usage principles.