Answer:
So, there isn't much of a transition word on sentence 16, but I feel like the word "Because" would work quite well. So the sentence would be changed to "Because tearing down the current stadium to build a new expensive one is not the right solution to the problem."
Explanation:
Now, there might be several different ways to work through this, might be several better answers, but I see the word "because" as something that explains why exactly tearing down the stadium would be a bad idea.