根际
参考答案：
靠近根系的那一部分土壤，也叫根-土界面，一般离根轴表面1mm至数毫米的范围。
闸板锁紧到位后，应回旋（）圈。
A、0.5～1
B、1／4～1／2
C、1～2
D、2—3
OSI is a theoretical model that shows how any two different systems can communicate with each other. Router, as a networking device, operate at the（）layer of the OSI model.
A.transport
B.application
C.network
D.physical
