Tigers are strong and dangerous animals. But now they are in danger. In the past, there were eight kinds of tigers in the world. But during the 20th century, only five were left. The number of Siberian tigers   was about 300, but now it is less than 22. They're in danger of dying out. If the government does nothing, we won't be able to see them in ten to twenty years. In order to stop people from hunting and killing wild tigers, and in order to make wild tigers more, the World Wildlife Fund   has started a program   recently  . China and twelve other countries joined it. However, it's not enough. Remember that nature is a food chain  . If we hurt and kill too many wild deer and pigs, wild tigers will die out because of hunger  . So the most important thing is to save the animals that tigers eat. In order to protect the wild tigers, we need call on   more people to stop eating, hunting and killing wild animals. ,. Wild tigers will be in danger of dying out without   _  .
pigs deer people A and B