Deconstruct the argument
-S: inflza sprd via comm air trvl => can cc/resch flight
- sym of inflza X visible before trvl
-cough sprd in encls/pcked envir
State the goal
Scientists stated that influenza is widely spread due to commercial air travel. It's probably that the symptoms of influenza develop while the person is on a plane, the infected person's cough can spread virus easily in the enclosed and closely packed environment. We need to find an answer that makes this scenario unlikely. There could be are ways to detect to prevent infected people from boarding the plane or way or something like that.
From wrong to right
(A) installing air filtration systems in the planes to kill any flu virus particles flowing through the filters
=>good to know, but not necessarily eliminate the spread of the virus
(B) requiring air travelers to receive flu vaccinations far enough in advance of the trip to provide protection against the disease
=> what we are looking for, this can prevent infected people from boarding the plane
(C) refusing to allow children, the elderly, or others who are especially vulnerable to flu to travel by air during a pandemic
=> B sounds more practical than this
(D) requiring all air travelers to wash their hands before boarding a plane
=> out of scope, the passage does not mention that washing hands can prevent influenza
(E) conducting medical examinations during the boarding process to weed out passengers with flu symptoms
=> Irrelevant, the passage is specifically talking about influenza
Answer: B