EXERCISE 9_GAP-FILL:

Read the text and choose A, B, C or D that best fits each of the numbered blanks, from 30 to 35
Both bacteria and viruses can cause diseases, ___(1)___. Bacteria are living organisms. They can live in many places, such as soil, water and the human body. The smallest bacteria are about 0.4 micron in diameter. Some bacteria in our bodies are helpful, but some can cause infectious diseases such as tuberculosis or food poisoning. ___(2)___.
Viruses are tiny germs that cause diseases in people, animals and plants. They can cause a range of illnesses, ___(3)___ to more serious diseases such as AIDS and Covid-19. As they are very small (0.02 to 0.25 micron), viruses can get into ___(4)___ easily. They are not living things, so they need to enter our bodies to become active. Then, they start to grow and cause the infected cell ___(5)___. Vaccines are often used to prevent ___(6)___.