为何无法解析域名，而只能解析域名服务器？高手帮忙！！！

hrbym

#more /var/named/db.test.com.cn \r\n; Created Fri Apr 16 17:52:07 CDT 1999 by services/ns-admin \r\n; \r\n@ IN SOA nsa.test.com.cn. root.test.com.cn. ( \r\n924252731 ; Serial Number \r\n10800 ; Refresh after 3 hours \r\n3600 ; Retry after 1 hour \r\n604800 ; Expire after 1 week \r\n86400 ) ; Minimum TTL of 1 day \r\n\r\n@IN NS nsa.test.com.cn. \r\nIN NS nsb.test.com.cn. \r\nIN MX 10 nsa.test.com.cn. \r\nIN MX 20 nsb.test.com.cn. \r\nnsa IN A 201.101.68.130 \r\nnsb IN A 201.101.68.131 \r\nwww IN A 211.91.133.15 \r\nlocalhost IN A 127.0.0.1 \r\n\r\n\r\n\r\n# nslookup test.com.cn \r\nServer: nsa.test.com.cn \r\nAddress: 201.101.68.130 \r\n\r\n*** test.com.cn can\'t find test.com.cn: Server failed \r\n# \r\n# nslookup nsa.test.com.cn \r\nServer:nsa. test.com.cn \r\nAddress: 201.101.68.130 \r\n\r\nNon-authoritative answer: \r\nName: nsa.test.com.cn \r\nAddress: 201.101.68.130 \r\n\r\n# \r\n\r\n\r\n\r\n问题：为何无法解析域名，而只能解析域名服务器？