题目

______ no bus, we had to walk home. A . There was B . There being C . Because there being D . There were 答案：B取高度分化的月季木质部细胞，经离体组织培养出月季幼苗，说明植物细胞 A．具有全能性 B．细胞分化后恢复原状 C．细胞癌变 D．细胞衰老