Apex domains cannot have CNAME records.
Question and response
Question
dig cernet.edu.cn. NS
Answer
cernet.edu.cn. 5 NS dns.edu.cn.
cernet.edu.cn. 5 NS dns2.edu.cn.
Authority
The response has no authority records.
Additional
dns.edu.cn. 5 A 202.38.109.35
dns2.edu.cn. 5 A 202.112.0.13
dns.edu.cn. 5 AAAA 2001:250:c006:0:0:0:0:35
dns2.edu.cn. 5 AAAA 2001:da8:1:100:0:0:0:13
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0