Question focus: Subordinate clauses and adverb clauses.
If we look at everything in this sentence, we will notice that we have a verb, loses, that does not have a subject. This is the only answer choice with a subject.
Still confused? Okay, in this sentence as is a preposition. Since every preposition must be followed by a noun (called its object), we need to have an object for the preposition. In this case, we have a noun clause as the object of the preposition.
You might still be confused. I explained this one to my students by telling them that as means the same thing (or almost the same thing) as like or for example.