Answer: their
Explanation: The sentence is addressing car buyers having something, in this instance a choice. When the subject is possessive, you use their. Such as, the car buyers ate <em>their</em> lunch.
The correct answer is that it is a dependent clause.
A dependent clause, as the name itself says, depends on a larger clause in order to make sense. As you can see in the example above, that clause is incomplete - it needs to be part of a larger, independent clause in order to get a proper meaning. The other options are all complete sentences, which is something the example is definitely not.
"valor without renown" means "bravery without honor"