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 Priesteria 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 that was blamed on Pfiesteria on North Carolina's Neusc River, ncarly 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.  

(Source: Michigan Proficiency)  

Question 35. What is true of Pfiesteria?  

      A. It has been a menace to fish and humans for over 3,000 years.  

      B. It seems to flourish in the presence of certain pollutants.  

      C. In large concentrations, it poses a threat to fish but not to humans.  

      D. It is the oldest life form on earth.  

Question 36. What is the main function of the toxins emitted by the dinoflagellates? 

      A. They weaken the fish just long enough for the tiny creatures to attack.  

      B. They cause fish to develop wounds on which the creatures feed.  

      C. They damage the nervous system of potential predators.  

      D. They are quick-acting poisons that kill fish within minutes.  

Question 37. The word “astounding" in the passage is closest in meaning to ___________

      A. apprehensive                   B. continual                          C. incredible                          D. spectacular 

Question 38. What were bulldozers used for in the Neuse River?  

      A. scooping up the vast number of dead fish in the water  

      B. excavating holes to bury the dead fish  

      C. removing the huge amount of Pfiesteria from the river  

      D. cleaning up the sediment at the bottom of the river  

Question 39. According to paragraph 2, what will NOT happen if one breathes the toxic air? 

      A. visual impairments                                                       B. circulatory difficulty  

      C. terrible headaches                                                        D. vomiting  

Question 40. What is especially worrying about Pfiesteria blooms?  

      A. Conditions are becoming increasingly favorable for their spread.  

      B. Researchers have no idea as to exactly what causes them.  

      C. They have devastated the fishing industry in U.S. coastal waters.  

      D. They are fatal to humans who come in contact with them.  

Question 41. All of the following are true, according to the passage, EXCEPT ___________

      A. the toxic substances emitted by Pfiesteria have a similar effect on human and fish skins. 

B. animal and chemical waste from farmlands, livestock and mining operations may contribute to the expansion of Pfiesteria.  

      C. Pfiesteria was not commonly noticed despite scientific findings.  

      D. Pfiesteria caused the death of about one billion fish in the late 1990s.  

Question 42. In which environment would you NOT expect a Pfiesteria bloom to develop? 

      A. a marsh which absorbs waste water from a nearby pig farm.  

      B. a cool mountain lake teaming with fish.  

      C. a river that flows through rich farmland.  

      D. a river located near a rock quarry.  

Đề thi thử THPT 2021 - Tiếng Anh - GV Vũ Thị Mai Phương - Đề 2 - có lời giải