Answer :
Answer: A) Although the sun was shining, it wasn't that warm.
Explanation: A subordinating conjunction is a connecting word or phrase with the function of introducing a dependent clause, joining it to a main clause. So in order to have a subordinating conjunction, we need to have a main clause and at least one dependent clause. From the given options, the only one that has two clauses, is option A, a main clause: "it wasn't that warm" and a dependent clause "although the sun was shining" with the subordinating conjunction "although."