1. If their habitat is threatened or they can’t find enough food, their numbers may decrease. 如果他们的栖息地受到威胁或者他们找不到足够的食物，他们的数目就可能减少。
The number of children in the school has decreased this year. 今年在校的儿童人数减少了。
There was a decrease in the number of children in school. 在校的儿童人数有所减少。
decrease in number 数目减少
2. As a result these endangered animals may even die out.结果，这些濒临危险的动物可能会灭绝。
The polluted air in the city is badly endangering the health of the residents.
城里被污染的空气正严重地危及居民的健康。
