[C]Slow-moving, hulking ships crisscross miles of ocean in a lawn mower pattern,wielding an array of 12 to 48 air guns blasting pressurized air repeatedly into the depths ofthe ocean. The sound waves hit the sea floor, penetrating miles into it, and bounce back tothe surface, where they are picked up by hydrophones. The acoustic patterns form athree-dimensional map of where oil and gas most likely lie.   The seismic air guns probably produce the loudest noise that humans use regularlyunderwater, and it is about to become far louder in the Atlantic. As part of the Trumpadministration’s plans to allow offshore drilling for gas and oil exploration, five companiesare in the process of seeking permits to carry out seismic mapping with the air guns all alongthe Eastern Seaboard, from Central Florida to the Northeast, for the first time in threedecades. The surveys haven’t started yet in the Atlantic, but now that the ban on offshoredrilling has been lifted, companies can be granted access to explore regions along the Gulf ofMexico and the Pacific   And air guns are now the most common method companies use to map the ocean floor.“They fire approximately every 10 seconds around the clock for months at a time,” saidDouglas Nowacek, a professor of marine conservation technology at Duke University. “Theyhave been detected 4,000 kilometers away. These are huge, huge impacts.”  The prospect of incessant underwater sonic tests is the latest example cited byenvironmentalists and others of the growing problem of ocean noise, spawning lawsuitsagainst some industries and governments as well as spurring more research into the potentialdangers for marine life.   Some scientists say the noises from air guns, ship sonar and general tanker traffic cancause the gradual or even outright death of sea creatures, from the giants to the tiniest —whales, dolphins, fish, squid, octopuses and even plankton. Other effects include impairinganimals’ hearing, cerebral hemorrhaging and the drowning out of communication soundsimportant for survival, experts say.   So great is the growing din in the world’s oceans that experts fear it is fundamentallydisrupting the marine ecosystem, diminishing populations of some species as the noise levelsdisturb feeding, reproduction and social behavior.   A 2017 study, for example, found that a loud blast, softer than the sound of a seismic airgun, killed nearly two-thirds of the zooplankton in three-quarters of a mile on either side.Tiny organisms at the bottom of the food chain, zooplankton provide a food source foreverything from great whales to shrimp. Krill, a tiny crustacean vital to whales and otheranimals, were especially hard hit, according to one study. “Researchers saw a completeabsence of life around the air gun,” said Michael Jasny, director of marine mammalprotection for the Natural Resources Defense Council, one of several environmental groupssuing the federal government in an effort to stop the seismic surveys.
53.What is a seismic air gun used for?
(A) To predict the coming of an earthquake.
(B) To investigate ocean creatures in US Eastern Seaboard.
(C) To keep the marine life out of the oil rig.
(D) To search for oil and gas under the ocean floor.