DNA的基本组成单位是[ ]
A.氨基酸
B.脱氧核苷酸
C.核糖核酸
D.脱氧核糖
答案:B
All people, ____they are old or young,black or white,all hold the same dream to have a peaceful world.
A.whether
B.however
C.no matter
D.even though
配置M断路器的ATS电源自动切换系统时需特别注意什么?