Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 33 to 37.

There has been an outbreak of avian influenza, better known as bird flu in Asia recently. The first (33) _____ died two weeks ago in Vietnam and there have been the cases reported since in Thailand, and there are some suspected cases in Cambodia as well as.

Wild birds are affected by a large number of flu viruses, just as the humans and other animals are, but they are normally exclusive to birds. If the viruses manage to mutate, they can to jump the species barrier and infect human beings. The first case (34) _____ someone died was in Hong Kong in 1997.

There are the several different forms of bird flu, ranging from mild to very (35) _____ infections, which spreading rapidly and kill many of the birds they infect. It is spread by wild birds-ducks, in particular – which carry the virus, but aren't killed by it. They can spread the virus to farm birds through (36) _____ contact or by the contaminating water supplies.

World Health Organization officials have attributed the spread of bird flu to human contact with the droppings of infected birds and (37) _____ sanitation. There was no evidence at first that the virus spread from person to person, though there has been a case of this happening being investigated by scientists.

Điền vào số (37)