Giải bởi Vietjack
Chức năng chính của các chất độc được phát ra bởi các chất tẩy rửa dinoflagellates là gì?
A. Chúng là chất độc nhanh chóng giết chết cá trong vòng vài phút.
B. Chúng làm suy yếu cá đủ dài để các sinh vật nhỏ xíu tấn công
C. Chúng phá hủy hệ thần kinh của những kẻ thù tiềm tàng.
D. Chúng làm cho cá phát triển vết thương các sinh vật gây nên
Dẫn chứng: The toxins eventually cause the fish to develop large bleeding sores through which the tiny creatures attack, feasting on blood and flesh.
Tạm dịch: Các chất độc cuối cùng khiến cá phát triển các vết loét chảy máu lớn qua đó các sinh vật nhỏ bé tấn công, ăn thịt và máu.
Chọn đáp án là: B
The example “You cant make a silk purse out of a sows ear” is used to...
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.
Pollution is a threat to many species on Earth, but sometimes it can cause species to thrive. Such is the case with Pfiesteria piscicida. A one-celled creature called a dinoflagellate, Pfiesteria inhabits warm coastal areas and river mouths, especially along the eastern United States. Although scientists have found evidence of Pfiesteria in 3,000-year-old sea floor sediments and dinoflagellates are thought to be one of the oldest life forms on earth, few people took notice of Pfiesteria.
Lately, however, blooms – or huge, dense populations – of Pfiesteria are appearing in coastal waters, and in such large concentrations the dinoflagellates become ruthless killers. The blooms emit powerful toxins that weaken and entrap fish that swim into the area. The toxins eventually cause the fish to develop large bleeding sores through which the tiny creatures attack, feasting on blood and flesh. Often the damage is astounding. During a 1991 fish kill, which was blamed on Pfiesteria on North Carolina’s Neuse River, nearly one billion fish died and bulldozers had to be brought in to clear the remains from the river. Of course, such events can have a devastating effect on commercially important fish, but that is just one way that Pfiesteria causes problems. The toxins it emits affect human skin in much the same way as they affect fish skin. Additionally, fisherman and others who have spent time near Pfiesteria blooms report that the toxins seem to get into the air, where once inhaled they affect the nervous system, causing severe headaches, blurred vision, nausea, breathing difficulty, short-term memory loss and even cognitive impairment.
For a while, it seemed that deadly Pfiesteria blooms were a threat only to North Carolina waters, but the problem seems to be spreading. More and more, conditions along the east coast seem to be favorable for Pfiesteria. Researchers suspect that pollutants such as animal waste from livestock operations, fertilizers washed from farmlands and waste water from mining operations have probably all combined to promote the growth of Pfiesteria in coastal waters.
What is true of Pfiesteria?
The word “astounding” in the passage is closest in meaning to _______.
Compared to preindustrial times, the number of hours in the workweek in the nineteenth century
The word "inevitably" in paragraph 2 is closest in meaning to____.
