Answer:
C). It is a group of related words.
Explanation:
The Phrase is defined as 'a group of words that functions as a single unit in the syntax of a sentence.' Such a group contains a set of related words that together convey a specific meaning however, it conveys an incomplete thought and 'cannot stand on its own.' It is an 'element of a clause' that requires the other elements to accomplish its meaning. Thus, option C is the correct answer.