In older commercial airplanes, the design of the control panel allows any changes in flight controls made by one member of the flight crew to be immediately viewed by the other crew members.
Statements
Comparative Distinction
In older planes, more so than newer planes, other crew members could more easily see when another member of the flight crew made some change in the flight controls.
Causal Connection (thereby)
Making it harder to observe other members' flight control changes eliminated a routine means for performing cross-checks.
Causal Connection (as a result)
Because they can no longer see the changes to flight controls made by other members of the team, members of flight crews verbally inform each other about what they're changing.
Evaluate
It's hard to say what the correct answer will go for here, but typically the correct answer reinforces Causal Connections, or spells out their implicit logic.
If making it harder to see others' changes eliminated a routine means for performing cross-checks, then we can infer that in older planes, members of the flight crew would routinely visually look at the flight controls to cross-check what other crew members were changing.
If depriving flight crews of a visual cross-check led to more verbal announcements of flight control changes, then we can infer that in older planes, members of the flight crew didn't feel as much need to announce the changes they were making.
Goal
Look for the most provable answer, being wary of Strong/Specific language, Out of Scope ideas, or Unknown Comparisons.