已知线段AB的端点B的坐标为（1，3），端点A在圆C：（x+1）²+y²=4上运动．

（1）求线段AB的中点M的轨迹；

（2）过B点的直线L与圆C有两个交点A，D．当CA⊥CD时，求L的斜率．

OSPF is a link-state routing protocol. It is designed to be run internal to a single (1) system. Each OSPF router maintains an identical(2) describing the autonomous system's topology. From this database, a routing table is calculated by constructing a shortest-path (3).OSPF recalculates routes quickly in the face of topological changes, utilizing aminimum of routing (4) traffic. OSPF provides support for equal-cost multipath. An area routing capability is provided, enabling.an additional level of routing protection and a reduction in routing protocol (5).

空白（4）处应选择（）

A.protocol

B.network

C.broadcast

D.multipath