單項(xiàng)選擇題The four-stroke cycle begins with the piston ().

A.coming up from the BDC
B.coming up from the TDC
C.coming down from the BDC
D.coming down from the TDC


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2.單項(xiàng)選擇題James Watt ()the steam engine in 1796.

A.discovered
B.had discovered
C.invented
D.had invented

3.單項(xiàng)選擇題Energy loses ()friction occurs in every engine.

A.because
B.thanks to
C.dues to
D.owing to