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词汇讲解：

1. obligation n.债务; 义务，责任
例句：We were under obligation to finish the work in a satisfactory way.
我们有义务圆满地完成工作。

2. settle vt.解决; 安排; 使定居
例句：After years of travel, we decided to settle here.
我们旅行多年后, 决定在此定居。

3. testify vi. 作证; 证明; 证实; 声明
例句：All of us can testify to his good behaviour.
我们都可以证明他表现很好。

4. override vt.覆盖; 推翻，无视
例句：The user is free to override the application’s decision if it is the wrong one.
如果错了，用户可以自由地更改程序的选择。

5. arrest vt.逮捕，拘捕; 止住
例句：A climate of fear would arrest a healthy maturation of diplomatic personnel.
胆战心惊的心理会妨碍外交人员的健康成长。

6. investigation n.侦查; （正式的） 调查，研究
例句：Many facts emerged as a result of the investigation.
调查结果,许多事实暴露出来。