甲、乙、丙、丁四个带电体,其中甲排斥乙,甲吸引丙,丙排斥丁,如果丁带的负电荷,则乙带的电荷是()。
A.正电荷;
B.负电荷;
C.中性的;
D.无法确定。
参考答案:A
By local doctors and nurses, we hope more people.
A.train, help
B.training, helping
C.training, to help
D.train, helping
磨煤机的合闸条件?