Read the following passage and mark the letter A, B, C, or D to indicate the correct word for each of the blanks.
BIRD FLU
There has been a(n) (41) ___________ of avian influenza, better known as bird flu in Asia recently. The first (42) ___________ died
two weeks ago in Vietnam and there have been cases reported since in Thailand, and there are some suspected cases in Cambodia (43) ___________.
Wild birds are affected by a large number of flu viruses, just as humans and other animals (44) ___________, but they are normally exclusive to birds. If the viruses manage to mutate, they can jump the species barrier and infect human beings. The first case (45) ___________ someone died was in Hong Kong in 1997.
There are several different forms of bird flu, raging from mild to very (46) ___________ infections, which spread rapidly and kill many of the birds they infect. It is spread by (47) ___________ birds-ducks, in particular - which carry the virus, but aren't killed by it. They can spread the virus to farm birds through (48) ___________ contact or by contaminating water supplies.
World Health Organization officials have attributed the spread of bird flu to human contact with the droppings of infected birds and (49) ___________ sanitation. There was no evidence at first that the virus spread from person to person, though there has been a (50) ___________ of this happening being investigated by scientists.
Trả lời câu hỏi dưới đây:
_________(45)