题目

—What day is it today?—_______. A . It's a fine day B . It's Friday C . It's July 1st D . It's hot today 答案：B 单倍体育种，可以明显地缩短育种年限，这是由于 [　　] A．培养技术操作简便 B．幼苗成活率高 C．单倍体植株生长迅速 D．后代不发生性状分离