In the theoretical frameworks of second language acquisition, Noam Chomsky's nativist paradigm and Stephen Krashen's Monitor Model offer distinct explanations for how human beings process and internalize a linguistic system. Consider the following four advanced propositions regarding these theories: I. Chomsky's Universal Grammar (UG) posits that humans are biologically endowed with an innate Language Acquisition Device (LAD) containing abstract, domain-specific linguistic principles and parameters that are triggered by primary linguistic input, enabling children to master complex syntactic structures rapidly despite impoverished stimulus. II. Krashen's Affective Filter Hypothesis asserts that emotional variables such as high anxiety, low self-confidence, and defensiveness raise a mental block that prevents 'comprehensible input' from reaching the language acquisition mechanisms, whereas a relaxed and motivated learner maintains a low affective filter. III. Krashen's Acquisition-Learning Hypothesis maintains that conscious grammar learning and subconscious language acquisition are functionally interchangeable processes; consequently, explicit formal classroom instruction can readily convert learned explicit rules into acquired implicit competence through sufficient mechanical drills. IV. The Input Hypothesis ($i+1$) suggests that language acquisition occurs when a learner is exposed to structured communicative input that contains grammatical structures slightly beyond their current level of competence, utilizing contextual meaning rather than explicit structural sequencing. Identify the option that correctly evaluates the theoretical, psycholinguistic, and pedagogical validity of propositions I, II, III, and IV according to second language acquisition theory and Language acquisition principles.