The answer for each sentence is:
1. We visited the shelter where many animals are waiting for homes: This is a COMPLEX SENTENCE. These kinds of sentences <u>are identified because they contain an independent clause and sometimes only one or at least one depend clause.
</u>
<em>Independent clause: we visited the shelter.
</em>
<em>Dependent clause: where many animals are waiting for homes.
</em>
2. We petted the cats, and they purred while dogs barked in the other room: this is a COMPLEX AND COMPOUND SENTENCE. Compound sentences <u>are identified because they usually have more than one subject and also because they have at least 2 independent clauses that are connected by a conjunction.
</u>
<em>The two subjects are: Cats and dogs.
</em>
<em>The conjunction is: While
</em>
3. The dogs wanted to play, and we took them to a dog park: This is a COMPOUND SENTENCE as I explained before and we can identify:
<em>The subject is: Dogs
</em>
<em>The conjunction is: And
</em>
4. We spent an hour at the park, which was packed, and then we left: this is a COMPOUND AND COMPLEX SENTENCE as I explained before. We can identify the following:
<em>Independent clause: We spent an hour at the park.
</em>
<em>Dependent clause: Which was packed, and then we left.
</em>
<em>The conjunction is: And </em>