Thirteen per cent of Christie's coin and banknote auction went unsold.佳士得13%的硬币和纸币拍卖流拍。I put the coin in the machine and pulled the lever.我把硬币投入机器，拉动控制杆。The golden rule is never to clean a valuable coin.重要的原则是决不清除贵重...
对偶体彼此相连于称为着丝粒的缩小的区域.The duplicates are attached to each other at a constricted region called the centromere.随着染色体的复制, 着丝粒始终连接着形成的两个染色单体.Following the replication of chromosomes, resultant chromatids remain attached at th...