Thanks for the question! So let’s take a look at the stimulus first. We’re told that a government agency publishes ratings of airline. The highest ranked airlines are those with the smallest proportion of late flights. And the point of making this ranking is to objectively measure the relative efficiency of different airlines’ personnel in being on time.
So now we’re asked for something that would invalidate use of the ratings for the agency’s purpose. In other words, something that suggests that this is a bad metric, that measuring the proportion of late flights is a bad way to tell the relative efficiency.
(D) tells us that what invalidates use of the ratings is that airline personnel know that the government agency is monitoring all airline flights for lateness. Sure, but if this is true, does it invalidate the argument? The fact that they’re being watched? If the proportion of late flights can measure the efficiency, it doesn’t matter if they’re being watched or not. It might change the results, but that’s fine.
Hope this helps! Feel free to ask any other questions that you might have.