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
; Created Fri Apr 16 17:52:07 CDT 1999 by services/ns-admin
;
@ IN SOA nsa.test.com.cn. root.test.com.cn. (
924252731 ; Serial Number
10800 ; Refresh after 3 hours
3600 ; Retry after 1 hour
604800 ; Expire after 1 week
86400 ) ; Minimum TTL of 1 day

@IN NS nsa.test.com.cn.
IN NS nsb.test.com.cn.
IN MX 10 nsa.test.com.cn.
IN MX 20 nsb.test.com.cn.
nsa IN A 201.101.68.130
nsb IN A 201.101.68.131
www IN A 211.91.133.15
localhost IN A 127.0.0.1



# nslookup test.com.cn
Server: nsa.test.com.cn
Address: 201.101.68.130

*** test.com.cn can't find test.com.cn: Server failed
#
# nslookup nsa.test.com.cn
Server:nsa. test.com.cn
Address: 201.101.68.130

Non-authoritative answer:
Name: nsa.test.com.cn
Address: 201.101.68.130

#



问题：为何无法解析域名，而只能解析域名服务器？