Our sunglasses block not only ultraviolet light, which is invisible and severely damaging to the eyes, but also the visible violet light that closest to ultraviolet light in the spectrum. Experiments have shown that this visible violet light can also be damaging to the eyes. Since all other sunglasses at best block only ultraviolet light, wearing our sunglasses will significantly improve eye protection for everyone who spends time outdoors.
Which of the following, if true, most seriously weakens the argument?
A Consumers who buy sunglasses are often more interested in the styling of the sunglasses' frames than in any potential protection to their eyes from the most harmful effects of sunlight.
B The visible violet light closest to ultraviolet light in the spectrum is not generally encountered at intensities strong enough to damage the eyes except under laboratory conditions.
C Wearing sunglasses that block the visible violet light closest to ultraviolet light in the spectrum will not appreciably affect the sharpness of people's visual images.
D The experiments mentioned in the advertisement were conducted at a major univer sity by professors who did not plan to have their research used in support of a commercial product.
E Some people who have not worn sunglasses on a regular basis enjoy excellent eyesight into advanced old age.
答案：B
In the past three summers, increasing numbers of migratory marine mammals have died in the Gordon City Bay area. It is now hypothesized that certain cleaning products for ships' hulls which contain the chemical LSA are responsible for the deaths. LSAt, which weakens mammals' defenses against infections, has been found in tissue samples from many of the dead animals and, significantly,the animals died of a viral infection not usually fatal to them.
Which of the following, if true, most strongly supports the hypothesis given?
A The cleaning products containing LSA came onto the market about four years ago and have, because of their superior effectiveness in cleaning ships' hulls, displaced the cleaners previously used.
B Tissue samples from the dead marine mammals have also been found to contain many substances other than LSA that are toxic to marine mammals.
C There are some indications that the virus that caused the deaths of marine mammals around Gordon City Bay has mutated in recent years into a more harmful form.
D Few of the marine mammals summering around Gordon City Bay ever stray into Gordon City harbor and its extensive seaport facilities.
E During the past three years in Gordon City Bay, there have been a number of fairly large fish kills in addition to increased deaths of marine mammals.
答案：A
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