多项选择题Which of the following descriptions about one carbon unit are right? A、One-carbon units are groups containing one carbon atom B、Be produced by amino acid catabolism C、All one carbon units can be interconverted with each other. D、One carbon unit can bind to the N5,N10 of FH4
单项选择题某建设工程施工项目招标文件要求中标人提交履约担保,中标人拒绝提交,则应( )。 A.按中标无效处理 B.视为放弃投标 C.按废标处理 D.视为放弃中标项目