阅读下面短文，用括号内所给词的适当形式或根据上下文内容填空(必要时可加情态动词或助动词)。
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 kinds of them were left. The number of Siberian tigers (东北虎) {#blank#}1{#/blank#}
(be) about 300, but now it is less than 22. They're in danger of {#blank#}2{#/blank#} (die)
out. If the government {#blank#}3{#/blank#} (do) nothing, we won't be able to see
them in ten to twenty years.
In
order to stop people from {#blank#}4{#/blank#} (hunt) and killing wild tigers, and in
order to make wild tigers more, the World Wildlife Fund (世界自然基金会) {#blank#}5{#/blank#}
(start) a program recently. China and twelve other countries joined it.
However,
it's not enough. Remember that nature is a food chain (链) . If we hurt and
kill too many wild deer and pigs, wild tigers {#blank#}6{#/blank#} (die) out because
of hunger. So the most important thing is {#blank#}7{#/blank#} (save) the animals
that tigers eat. In order to protect the wild tigers, we need to call on (号召) more people to stop eating, hunting and killing wild animals.
