Which port must be opened to correct this specific problem?

After successfully adding a new ESXi 6.x host to vCenter Server, an administrator sees it as Not Responding in the vSphere Web Client interface a few minutes later.
If the issue is caused by a network firewall blocking traffic, which port must be opened to correct this specific problem?
A. 443 (TCP)
B. 443 (UDP)
C. 902 (TCP)
D. 902 (UDP)