Answer:
I took the dog for a walk in the park because he had been shut in the house all day. → complex
He stopped to bark at several other dogs, and he chased a squirrel. → compound
We completed a half-mile walk. → simple
When we got home we were both tired; however, only the dog could take a nap. → compound
Step-by-step explanation:
We say a sentence is simple when it is formed by a single independent clause. Let's remember that an independent clause has a subject and a predicate, and it is able to stand alone and express a complete thought.
A compound sentence is formed when we put together two independent clauses. They are usually connected by a coordinating conjunction (and, but, or, yet, etc.). But, as we can see in the last sentence above, "however" can also be used to introduce another independent clause in the sentence.
Finally, a complex sentence is formed by joining an independent clause and a dependent or subordinate one. They are connected by subordinating conjunctions, such as "because", "after", "while", etc.