1. It is disturbing to think that a dangerous wild animal is still at large in the quiet countryside.
    想到在宁静的乡村里有一头危险的野兽继续逍遥流窜，真令人担心。

2. Is cloning morally wrong and dangerous — or is it a valuable research tool?
    克隆是违背或危害道德的——还是一种有价值的研究手段？

3. For hundreds of years, St. Bernard dogs have saved the lives of travellers crossing the dangerous Pass.
    几百年来，圣伯纳德修道院驯养狗拯救了许多翻越这道山口的旅游者的生命。

4. For instance, tuberculosis, once a dangerous killer, was cured. Now the disease is appearing again.
    例如，曾经是危险杀手的肺结核原本已被消灭，但是现在这种疾病又死灰复燃了。