The correct answer is A) the environment.
The issue that was seen as the centerpiece of candidate Al Gore's campaign in the 2000 presidential election was the environment.
Former United States vice president Al Gore was the Democratic candidate for the US presidency of 2000. His rival was George W. Bush, who resulted in victorious in the controversial election. As a candidate during his political campaign, Al Gore showed a deep concern about the environment and the effects of global warming. Indeed, years later, he sponsored a documentary called "An Inconvenient Truth," which exposes many issues that affect the environment.