Apex domains cannot have CNAME records.
Question and response
Question
dig client.thehost.ua. NS
Answer
client.thehost.ua. 5 NS ns4.thehost.pro.
client.thehost.ua. 5 NS ns3.thehost.biz.
client.thehost.ua. 5 NS ns1.thehost.ua.
client.thehost.ua. 5 NS ns2.thehost.net.
Authority
The response has no authority records.
Additional
ns1.thehost.ua. 5 A 91.223.180.14
ns1.thehost.ua. 5 AAAA 2a0c:f00:0:0:0:0:1:14
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0