Read the following passage and mark the letter A, B, C, or D to indicate the answer to each of the question.
Covering more than 70 percent of our planet, oceans are among the earth’s most valuable natural resources. They govern the weather, clean the air, help feed the world, and provide a living for millions. They also are home to most of the life on earth, from microscopic algae to the blue whale, the largest animal on the planet. Yet we’re bombarding them with pollution. By their very nature—with all streams flowing to rivers, all rivers leading to the sea—the oceans are the end point for so much of the pollution we produce on land, however far from the coasts we may be. And from dangerous carbon emissions to choking plastic to leaking oil to constant noise, the types of ocean pollution humans generate are vast. As a result, collectively, our impact on the seas is degrading their health at an alarming rate. Here are some ocean pollution facts that everyone on our blue planet ought to know.
When we burn fossil fuels, we don’t pollute just the air but the oceans, too. Indeed, today’s seas absorb as much as a quarter of all man-made carbon emissions, which changes the pH of surface waters and leads to acidification. This problem is rapidly worsening—oceans are now acidifying faster than they have in some 300 million years. It’s estimated that by the end of this century, if we keep pace with our current emissions practices, the surface waters of the ocean could be nearly 150 percent more acidic than they are now.
The majority of the garbage that enters the ocean each year is plastic—and here to stay. That’s because unlike other trash, the single-use grocery bags, water bottles, drinking straws, and yogurt containers, among eight million metric tons of the plastic items we toss (instead of recycle), won’t biodegrade. Instead, they can persist in the environment for a millennium, polluting our beaches, entangling marine life, and getting ingested by fish and seabirds.
Where does all this debris originate? While some is dumped directly into the seas, an estimated 80 percent of marine litter makes its way there gradually from land-based sources―including those far inland―via storm drains, sewers, and other routes. Oil from boats, airplanes, cars, trucks, and even lawn mowers is also swimming in ocean waters. Chemical discharges from factories, raw sewage overflow from water treatment systems, and storm water and agricultural runoff add other forms of marine-poisoning pollutants to the toxic brew.
The ocean is far from a “silent world.” Sound waves travel farther and faster in the sea’s dark depths than they do in the air, and many marine mammals like whales and dolphins, in addition to fish and other sea creatures, rely on communication by sound to find food, mate, and navigate. But an increasing barrage of human-generated ocean noise pollution is altering the underwater acoustic landscape, harming—and even killing—marine species worldwide.
Which of the following could best reflect the main idea of the passage?
