The term "virus" is derived from the Latin word for poison or slime. It was originally applied to the noxious stench emanating from swamps that was thought to cause a variety of diseases in the centuries before microbes were discovered and specifically linked to illness. But it was not until almost the end of the nineteenth century that a true virus was proven to be the cause of a disease.  

      The nature of viruses made them impossible to detect for many years even after bacteria had been discovered and studied. Not only are viruses too small to be seen with a light microscope, they also cannot be detected through their biological activity, except as it occurs in conjunction with other organisms. In fact, viruses show no traces of biological activity by themselves. Unlike bacteria, they are not living agents in the strictest sense Viruses are very simple pieces of organic material composed only of nucleic acid, either DNA or RNA, enclosed in a coat of protein made up of simple structural units (some viruses also contain carbohydrates and lipids.) They are parasites, requiring human, animal, or plant cells to live. The virus replicates by attaching to a cell and injecting its nucleic acid. Once inside the cell, the DNA or RNA that contains the virus' genetic information takes over the cell's biological machinery, and the cell begins to manufacture viral proteins rather than its own.  

Question 30. Which of the following is the best title for the passage?  

      A. New Developments in Viral Research                         B. Exploring the Causes of Disease 

      C. DNA: Nature's Building Block                                    D. Understanding Viruses  

Question 31. Before microbes were discovered, it was believed that some diseases were caused by 

      A. germ-carrying insects                                                  B. certain strains of bacteria  

      C. foul odors released from swamps                                D. slimy creatures living near swamps 

Question 32. The word “proven" is closest meaning to which of the following? 

      A. shown                              B. eared                                C. imagined                         D. considered 

Question 33. The author implies that bacteria were investigated earlier than viruses because___________

      A. bacteria are easier to detect                                         B. bacteria are harder to eradicate 

      C. viruses are extremely poisonous                                  D viruses are found only in hot climates 

Question 34. All of the following may be components of a virus EXCEPT___________

      A. RNA                                B. plant cells                        C. carbohydrates                  D. a coat of protein 

Đề thi thử THPT 2021 - Tiếng Anh - GV Vũ Thị Mai Phương - Đề 12 - có lời giải