大学英语：An animal species becomes(虽然species是以s结尾

　　1. An animal species becomes(虽然species是以s结尾，但此处该词跟在冠次an后，还是单数，所以谓语become用了单数) extinct when it fails to produce enough young in each generation to keep pace with the death rate.

　　2. Better-adapted 更能适应环境的

　　3. A number of examples can be given of the way in which(定于从句之所以用in which，是因为in the way表示以某种方式) natural environments are being rapidly changed.

　　4. Likelihood 可能性

　　5. Because表示因为是连词，后面应该接句子;because of 表示因为是介词短语，后加名词或代词。

　　6. Provided(that)+从句，表示如果

　　7. There is great pleasure in watching wildlife in natural or near-natural environments.

　　Text B The killer Smogs