可燃基挥发分高的煤种是焦煤。
参考答案：错
四个质点作直线运动，它们的速度图象分别如图所示，在2s末能回到出发点的是（ ）
A．
B．
C．
D．
A lot of research and studies have shown that Trench oil, taken out from kitchen waste, ______ the increase of cancers.
A．results from
B．attends to
C．contributes to
D．devotes to
