第 16 至 20 題為題組        Airline passengers may have noticed that all plane windows have rounded edges, instead of the hardcorners commonly found in our house. The round windows are indeed pleasant to the eye, but they actuallywere designed for reasons __16__ aesthetics.
         In the early days of aviation, plane windows __17__ square in shape. Then as commercial air travelbecame popular in the 1950s and airplanes began flying higher and faster, three planes mysteriously brokeapart in midair. The cause? Square windows. Scientists found that sharp corners are natural weak spotswhere stress concentrates. The problem is __18__ when airplanes fly at higher altitudes, where thedifference between the inside and outside pressure increases, causing added stress. When subjected torepeated pressurization high in the sky, the four corners on a square window may __19__ .        Curved windows, on the other hand, distribute stress around more evenly, reducing the likelihood ofcracks or breaks. Circular shapes are also stronger and resist deformation, and therefore can 20 extremedifferences in pressure inside and outside of an aircraft.         Thus, round windows are a major safety innovation that keeps planes from disintegrating mid-flight.They are also used on ships and spacecraft for their greater structural integrity.
【題組】16.
(A) contrary to
(B) except for
(C) more of
(D) other than