III. Reading Comprehension (8%)
      Around the world, governments and automakers are promoting electric vehicles as a key technology
to curb oil use and fight climate change. As electric cars and trucks go mainstream, however, they have faced a persistent question: Are they really as green as advertised? While experts broadly agree that electric vehicles are a more climate friendly option than traditional vehicles, they can still have their own
environmental impacts, depending on how they’re charged up and manufactured.
      Broadly speaking, most electric cars sold today tend to produce significantly fewer planet-warming
emissions than most cars fueled with gasoline. But a lot depends on how much coal is being burned to
charge up those    plug-in vehicles   . An all-electric Chevrolet Bolt, for instance, can be expected to produce 189 grams of carbon dioxide for every mile driven over its lifetime. By contrast, a new gasoline-fueled Toyota Camry is estimated to produce 385 grams of carbon dioxide per mile. A new Ford F-150 pickup truck, which is even less fuel-efficient, produces 636 grams of carbon dioxide per mile. On the other hand, if the Bolt is charged up on a coal-heavy grid, such as those currently found in the Midwest, it can actually be a bit worse for the climate than a modern hybrid car like the Toyota Prius, which runs on gasoline but uses a battery to bolster its mileage. (The coal-powered Bolt would still beat the Camry and the F-150, however.)
      “Coal tends to be the critical factor,” said Jeremy Michalek, a professor of engineering at Carnegie
Mellon University. “If you’ve got electric cars in Pittsburgh that are being plugged in at night and leading
nearby coal plants to burn more coal to charge them, then the climate benefits won’t be as great, and you can even get more air pollution.”      Raw materials used to manufacture electric vehicles can also be problematic. Like many other batteries, the lithium-ion cells that power most electric vehicles rely on raw materials — like cobalt, lithium and rare earth elements — that have been linked to grave environmental and human rights concerns. Cobalt has been especially problematic. Mining cobalt produces hazardous tailings and slag that can leach into the environment, and studies have found high exposure in nearby communities, especially among children, to cobalt and other metals. At present, as much as 70 percent of the world’s cobalt supply is mined in the Democratic Republic of Congo, a substantial proportion in unregulated mines where workers — including many children — dig the metal from the earth using only hand tools at great risk to their health and safety.
      To deal with the problem, automakers have committed to eliminating    “artisanal”    cobalt from their
supply chains, and have also said they will develop batteries that decrease, or do away with, cobalt
altogether. But that technology is still in development, and the prevalence of these mines means these
commitments “aren’t realistic,” said Mickaël Daudin of Pact, a nonprofit organization that works with mining communities in Africa. Instead, Mr. Daudin said, manufacturers need to work with these mines to lessen their environmental footprint and make sure miners are working in safe conditions. Green as they seem,there is still much room for improvement for these electric cars.
【題組】23. What is the purpose of this passage?
(A) To evaluate electric cars.
(B) To provide a solution to climate change.
(C) To promote green vehicles.
(D) To warn against cobalt mining.