The answer is B. Given this.
Signal words (also called transitions) help connect ideas inside the structure of a text. There are many types of signal words, for instance: comparison words, contrast words, emphasis words and so on.
In the excerpt asked about, we have the expression "given this", which connects the idea that is about to be developed with the ideas and arguments that have already been pointed out in the previous paragraphs. This is expression signals a relationship of cause and effect. Given ... circumstances, we have... results.