Complete the sentence: A tuberculin skin test should be read within 24 hours ____ administration.

The correct choice, "of," is appropriate in this context because it indicates a relationship in time and is used to show the point in time at which something occurs. In this case, "should be read within 24 hours of administration" specifies the timeframe for reading the result of the tuberculin skin test.

Using "of" effectively links the act of reading the test to the specific event of its administration, clarifying that the reading should take place within a 24-hour period that begins at the moment the test is given. This phrasing is standard in medical and professional communication, emphasizing the importance of specific timing in procedural contexts.