Complete Question Explanation
Must Be True. The correct answer choice is (E)
Here the author explains that the control panel design in commercial airplanes has changed over time. In older planes, any flight control changes made by a crew member were immediately visible to all other crew members. In newer planes, this automatic cross-check is not available, necessitating that crew members inform each other verbally of such changes much more frequently.
Answer choice (A): There is no discussion of how long it takes to perform control changes, so this answer choice is unsupported by the stimulus.
Answer choice (B): While verbal informing was indeed one available cross check, there is no basis for the assertion that it was the most valuable means available, so this answer choice is incorrect.
Answer choice (C): While such checks were required less frequently, this answer choice goes too far with the phrase “no need to exchange information.” Since this choice fails the Fact Test, it is incorrect.
Answer choice (D): Perhaps they can monitor changes if they constantly watch the control panel, but the distinction is that they can no longer immediately see all such changes.
Answer choice (E): This is the correct answer choice. Since the lack of one cross check necessitates more frequent verbal informing, it is valid to infer that this answer choice is accurate according to the stimulus.