Answer: 2nd option (After giving it a lot of thought, Jackie decided to adopt a dog instead of buying from a breeder)
Step-by-step explanation:
A subordinate conjunction is a word or a phrase that connects a dependent clause to an independent clause, subordinate conjunctions are used at the beginning of a sentence.
12 subordinate conjunctions are as follows:
After, although, as, as if, because, before, how, if, since, than, though, unless, until, when, where and while.