backend语句块中，以下加入内部节点主机的语句，正确的是：
Aserver web1 192.168.10.100:8080 checked weight=20
Bserver web1 192.168.10.100:8080 check weight 20
Cserver web1 192.168.10.100 check weight=20
Dserver web1 192.168.10.100:8080 checked weight 20
Aserver web1 192.168.10.100:8080 checked weight=20
Bserver web1 192.168.10.100:8080 check weight 20
Cserver web1 192.168.10.100 check weight=20
Dserver web1 192.168.10.100:8080 checked weight 20