简述地图色彩的特点。
参考答案：
①她图色彩大多以均匀色层为主；
②色彩使用的系统性；
③地图色彩的制约性；
④色彩意义的明确性。
当今世界上的三大化石燃料中，被称为“工业的血液的”是______；被称为“工业的粮食的”是______．
A “liner” in riveted construction of a vessel is a(n)（）.
A.small plate which fills the aperture between riveted strakes and the vessel framing
B.backing plate which is used to level the strakes while riveting，and then removed
C.internal frame to which the side shell is riveted
D.seam that is welded after riveting is completed
