Wear in a cylinder liner is usually due to ___________.
A. friction
B. abrasion
C. corrosion
D. all of the others
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The crankshaft should be turned by means of ____ to see that all parts move freely.
A. a steering gear
B. a chain gear
C. a turning gear
D. a sever motor
将下列段落翻译成汉语:A transponder is an electronic device that produces a response when it receives a radio-frequency interrogation. In aviation, aircraft have transponders to assist in identifying them on radar and on other aircraft's collision avoidance systems. Air traffic control units use the term "squawk" when they are assigning an aircraft a transponder code, e.g. "Squawk 7421". Squawk or squawking thus can be said to mean "select transponder code" or "I have selected transponder code xxxx"
将下列段落翻译成汉语:Depending on the type of interrogation, the transponder sends back a transponder code (Mode A) or altitude information (Mode C) to help air traffic controllers to identify the aircraft and to maintain separation. Another mode called Mode S (Mode Select) is designed to help avoiding over-interrogation of the transponder (having many radars in busy areas) and to allow automatic collision avoidance.
将下列段落翻译成汉语:Secondary Surveillance Radar is referred to as "secondary", to distinguish it from the "primary radar" that works by passively bouncing a radio signal off the skin of the aircraft. Primary radar works best with large all-metal aircraft, but not so well on small, composite aircraft. Its range is also limited by terrain and rain or snow and also detects unwanted objects such as automobiles, hills and trees. Furthermore not all primary radars can estimate the altitude of an aircraft.