各种动物的数量在自然生态系统中[ ]

A．固定不变

B．缺少天敌时可无限增长

C．不受人为因素的影响

D．由于食物、空间及天敌的制约，不可能无限增长

NAC’s (Network Access Control) role is to restrict network access to only compliant endpoints and (66) users. However, NAC is not a complete LAN (67) solution; additional proactive and (68) security measures must be implemented. Nevis is the first and only comprehensive LAN security solution that combines deep security processing of every packet at 100Gbps, ensuring a high level of security plus application availability and performance. Nevis integrates NAC as the first line of LAN security (69) In addition to NAC, enterprises need to implement role-based network access control as well as critical proactive security measures-real-time, multilevel (70) inspection and microsecond threat containment.

（69）是（）

A.defense

B.intrusion

C.inbreak

D.protection