The correct option is A Henry VIII was the first English king of Ireland.
According to general rule, the first word of a sentence is always capitalized. Capitals are used for all proper nouns in a sentence or the words derived from proper nouns, like 'English'.
As a rule, if roman numbers in a sentence refer to a person or place, it must be capitalized.
Thus, according to rules, the correct answer is Option A. The remaining options are incorrect.