The answer is D, they worked to expose the corrupt businesses like Boss Tweed.
I'm not exactly sure how to answer that for you, but you can use the attached file to pin-point what you are looking for.
Is there a paper you can take a picture of
I believe the answer is: Reliability
Reliability in this context refers to the ability to provide consistent and accurate information in order to know the true difference before and after using the drugs, otherwise the data collected by Andrea would be inadmissible and it would mess up the whole research.<span />