Which of the following is a subordinate clause?

None that I can see.

To answer this question, we need to understand what a subordinate clause is. A subordinate clause is a clause that cannot stand alone as a complete sentence and functions as a dependent clause within a sentence. It often begins with a subordinating conjunction such as "because," "since," "although," "when," etc.

Now, let's look at the options provided and identify the subordinate clause:

1) "She went to the store"
2) "Although it was raining"
3) "The dog ran to the park"
4) "He waved goodbye to his friends"

Out of these options, the second one, "Although it was raining," is a subordinate clause. It starts with the subordinating conjunction "although" and cannot stand alone as a complete sentence.