The answer is : the introduction
Sensible is the answer you are looking foe
The second point in the paragraph about children provides more support for the overall topic: noise pollution. because it's offering more evidence that noise pollution is an issue, "furthermore" is your best choice as a transition. "for instance" would suggest that you're giving an example of something, as in a specific case in which a child's education suffered. "however" suggests a shift, usually describing an exception, and the point of the children's education is not an exception--it's further evidence. "consequently" suggests that you'd carry on to tell the reader about an effect of a circumstance.
