There are different sections to the TSA computer-based test. The most difficult section of the test is the X-ray test, where you are challenged to recognize dangerous objects within 15 seconds. This task is difficult as many times the objects are laid in a position that makes it difficult to recognize the outline of the object. In addition, other objects in the bag may hide or cover up portions of the object. Only about 30% of test takers pass this section of the test, which is required if you want to work as a transportation security officer. Those who do pass the test are occasionally required to take the test multiple times to ensure that they maintain their threat identification skills.