GNU make 工具在当前工作目录按什么顺序搜索makefile？ A: GNU Makefile ,makefile,Makefile B: GNUmakefile ,makefile,Makefile C: makefile,GNUmakefile ,Makefile D: Makefile ,makefile,GNUmakefile

以下( )都是合法的makefile文件 A: GNUmakefile B: makefile C: Makefile D: MAKEFILE