The word "boomerang" (boldfaced in Paragraph 1) refers to （）

A. There is a reported competition among elevator operators in Hong Kong, with some buildings opting to contract elevator maintenance to firms that offer low rates.
B. The Housing Authority has said that all of its elevators are maintained by the original manufacturer (in Hong Kong’s case, by "Schindler Lifts Hong Kong Limited") and all elevators are inspected fully once every week.
C. It should be noted that elevator maintenance had been carried out by a Japanese maintenance company and not by Schindler since 2005.
D. That elevators are not infallible came as a surprise to many people, especially when it was discovered that of the 8,800 Schindler elevators installed in Japan, 85 have trapped people.
E. Japan has already ordered full inspections of the country’s entire set of Schindler elevators, with elevators of all manufacturers being inspected in government buildings.
F. Public concern over the Minato case has not been limited merely to Schindler elevators.

A. Then, when they keep taking sick days from work when they grow up, we wonder why.
B. It’s natural to look for the weak link in this chain of disaster and, not unusually, it’s teachers who are being criticized.
C. This translates all too quickly into orders unfulfilled and contracts prejudiced.
D. Quite frankly, I don’t blame thousands of teachers eagerly taking a couple of days off when faced in front by mob of badly behaved, obese and foul-mouthed children.
E. For the want of some sand for the roads, ￡3.5bn was lost.
F. And it seems unfair of impose our comfortable, schoolroom nostalgia on a profession facing peculiar contemporary challenges.