VLAN互联，基本上有边界路由、“独臂”路由器、路由服务器/路由客户机、ATM上的多协议（MPOA）路由和（ ）
A.中心路由
B.核心路由
C.多层路由
D.第三层交换
正确答案是D
Complete each of the following sentences with a (compound) word derived from the one(s) given in brackets.
The couple expressed their （ ）thanks to the young man who had saved their son by donating one of his kidneys.(heart,feel)
