The strategy that would make use of your previous knowledge would be that of "guessing from context." When you are reading a text, and you do not understand something (a word, a situation, an event, etc.) one of the things that you can do is try to guess. A guess can be quite accurate if you pay attention to the context of the text. However, in order to be able to do this, you would need to rely on your prior knowledge.
The main purpose of the detail is to show that recycling is important. Statistic shown by B can help show that recycling is not deemed important but should be.
