Answer: The transition word that best connects the ideas included in the paragraph is A. therefore.
Step-by-step explanation: Transition words are generally included to give more coherence to a text or to show the reader which are the logical relationships that connect phrases or sentences. One of those transition words is "therefore", which means "as a consequence" or "for that reason". Furthermore, "therefore" is the best option to fill in the gap because the paragraph presents a cause and an effect. The cause is the recent awareness that our environmental choices affect in a negative way the lives of "our neighbours across the ocean", while the effect is the idea that people should start working together in order to make changes and create a better future for all.