Every complete sentence contains two parts: a subject and a predicate. It describes only one thing, idea or question, and has only one verb.
To determine the subject of a sentence, first isolate the verb and then make a question by placing “who?” or “what?” before it — the answer is the subject.
The predicate (which always includes the verb) goes on to relate something about the subject.
Note: Questions and sentences in Spanish are the same, except you add the question mark
1) Perdón, Usted habla español?
So first isolate the verb habla. Who speaks English? Usted
Therefore Usted is the Subject. What about the subject?