The answer is letter B-- phrase.
A phrase referes to a group of words that act as one
unit or a single part of speech in a sentence. It doesn't have both a subject and a verb, yet it acts as either a subject or a verb. It's a part of a sentence which doesn't express a complete thought.
For example:
The beautiful house down the road is owned by my teacher.
The noun phrase is-- The beautiful house down the road
The verb phrase is-- owned by my teacher
These are the phrases of these sentences which cannot stand alone.