Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

By mid-century, there will likely be 9 billion people on the planet, consuming ever more resources and leading ever more technologically complex lives. What will our cities be like? How much will artificial intelligence advance? Will global warming trigger catastrophic changes, or will we be able to engineer our way out of the climate change crisis?

Making predictions is, by nature, a dicey business, but to celebrate the 40th anniversary of Smithsonian magazine Big Think asked top minds from a variety of fields to weigh in on what the future holds 40 years from now. The result is our latest special series, Life in 2050. Demographic changes in world population and population growth will certainly be dramatic. Rockefeller University mathematical biologist Joel Cohen says it's likely that by 2050 the majority of the people in the world will live in urban areas, and will have a significantly higher average age than people today. Cities theorist Richard Florida thinks urbanization trends will reinvent the education system of the United States, making our economy less real estate driven and erasing the divisions between home and work.

Large migrations from developing countries like Indonesia, Malaysia, Bangladesh, Mexico, and countries in the Middle East could disrupt western governments and harm the unity of France, Germany, Spain, the Netherlands, Poland, and the United Kingdom under the umbrella of the European Union.

And rapidly advancing technology will continue ever more rapidly. According to Bill Mitchell, the late director of MIT's Smart Cities research group, cities of the future won't look like "some sort of science-fiction fantasy" or "Star Trek" but it's likely that "discreet, unobtrusive" technological advances and information overlays, i.e. virtual reality and augmented reality, will change how we live in significant ways. Self-driving cars will make the roads safer, drive more efficiently, and provide faster transports. A larger version of driverless cars—driverless trucks—may make long-haul drivers obsolete.

Meanwhile, the Internet will continue to radically transform media, destroying the traditional model of what a news organization is, says author and former New York Times Public Editor, Daniel Okrent, who believes the most common kinds of news organizations in the future will be "individuals and small alliances of individuals" reporting and publishing on niche topics.

The word “trigger” in the first paragraph could be best replaced by _____________.