Answer:
a hyphen separates a prefix ending in a vowel from a root word beginning with a vowel; a dash does not
Step-by-step explanation:
You should use a hyphen to connect a prefix to another word if the prefix ends in a vowel and the base word also begins with one.
e.g. "pre-eminent," “co-own,” "anti-immune".
You cannot use a dash with these words.