99色精品-9色在线-99色在线-99色视频国产欧美日产一区二区三区_亚洲精品亚洲人成在线观看_四虎在线精品永久观看_免费一级a一片久久精

單項選擇題

James Watt （）the steam engine in 1796.

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

你可能感興趣的試題

單項選擇題

Energy loses （）friction occurs in every engine.

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

單項選擇題

The mechanical efficiency of an engine is always less than 100% （） losses occurring in the form friction.

A.because
B.since
C.due to
D.owing to

<em id="r7a7a"><noframes id="r7a7a"><ins id="r7a7a"></ins>