The prefix ‘inter’ signifies a relationship ‘between’ two or more entities, as in the word 'interstate', referring to actions or things involving two or more states. Similarly, the prefix ‘intra’ describes something occurring ‘within’ a single entity. For example, 'intravenous' refers to something occurring within or administered through a vein. Therefore, when given the options:
The correct option to fill in the blank for the meaning of ‘intra’ is: within.