Regarding the verb structure and meaning of the excerpt "Japan has probably been occupied for at least 30,000 years, if not longer" from the text, judge the statements below.

I.The structure "have probably been occupied" is in the present perfect passive and suggests cautious probability, while "if not longer" extends the stated time span beyond the minimum mentioned.

II.The adverb "probably" expresses absolute certainty and shows that the author presents the information as an unquestionable fact.

III.The expression "if not longer" restricts the occupation period to exactly 30,000 years.

Which proposition(s) is/are CORRECT?