19. Perhaps no issues are more controversial than euthanasia and abortion , both of which involve taking the life of a human being .
也许没有问题比安乐死和人工流产更有争议性，它们都涉及结束一个人的生命。
20. Never before in history has the issue of overpopulation been more evident than now .
历史上，人口过剩的问题从来没有比现在更加突出。