The correct answer is B. A clause has a subject and a verb; a phrase does not. This is correct because any time a phrase has a verb added to it it becomes a clause. An example could be a noun phrase "The hardworking man". If you add a verb "sleeps" to it, it becomes a clause "The hardworking man sleeps".
I like this car but doesn't it seem a little old for me?
Or you can use:
This is a nice car but I don't want it to break down on me.
It is a requirement to pass your classes to graduate.
