Final answer:
The bolded word group 'even for identical twins' lacks both a subject and a verb, and is thus classified as a. phrase, not a clause.
Step-by-step explanation:
The bolded word group 'even for identical twins' is a phrase because it does not have both a subject and a verb, hence it cannot be considered a clause. According to the definitions provided, a phrase may function as a unit within a sentence but it lacks either a subject or a verb. On the other hand, a clause is a group of words that includes both a subject and a verb. Clauses can be independent, being able to stand alone as a sentence, or dependent, where they cannot.
In the context of identical twins, although they may have identical genes at the point of conception, it is their exposure to different environments over their lifetimes that contributes to their unique fingerprints. This concept also applies to the principle of DNA fingerprinting which is used to determine whether two DNA samples come from related individuals or not. Therefore, the correct option in the final answer for whether the bolded word group is a phrase or a clause is: a. Phrase.