This element is the product of adding a root to a combining vowel prefix
suffix
root
combining form

combining form

Explanation:

Combining Form is a medical-related that describes a compound word which is an outcome of the addition of a word root and a combining vowel. In some other cases, it can be a result of a word root and a suffix that starts with a consonant.

Hence, in this case, the correct answer is COMBINING FORM is the element that happens to be the product of adding a root to a combining vowel