1. But the cause of malaria remained unknown to 17th-century medicine, and so there was investigation by experiment.
    但对于17世纪的医学来说，疟疾的起因仍属未知，所以便通过实验来进行调查。

2. The investigation revealed no impropriety.
    调查表明没有不正当的做法.

3. This problem is still under investigation.
    这个问题仍在调查中。

4. The inner workings of our own brains we feel to be uniquely worthy of investigation,
    我们觉得，只有我们大脑内部的活动情况才值得研究，

5. This is no abstract investigation.
    这决不是抽象的调查。

6. Regard any investigation of this question as a waste of time;
    他们认为对这个问题进行调查中浪费时间，

7. Investigation exculpated him from the suspicion of having caused the accident.
    调查结果已排除了他造成此次车祸的嫌疑。

8. For example, one U.S. corporation offered a large sum of money in support of a U.S. presidential candidate at a time when the company was under investigation for possible violations of U. S. business laws.
    比如，有一家美国企业曾因可能触犯美国商业法规而正受调查，此时它捐出一大笔款项支持一位总统候选人。