What law did congress pass to ensure "reasonable and just" railroad rates?

The Interstate Commerce Act of 1887 regulated the railroad industry to avoid its' monopolistic practices. The government did not set specific prices but stated that they needed to be reasonable and just. It prohibited price discrimination which affected mostly small markets. The government required railroads to make public their shipping rates.  It also created the Interstate Commerce Commission which was a federal organization that would monitor railroads.  

answer:

d. because dr. laguardia selected a widely used measure, his study generalizes to has strong external validity. external validity has limited external validity. other applications of this measure.

the widely used measure that he applied to his experiment was the benton facial recognition test. it employed on to football players and as result, only players who suffered brain concussions did not pas this test. and although it has an external validity, it is limited because it isn't general to apply to other population.

dude you should crop your image so only the question shows. but   can you explain it better