A server technician is configuring the IP address on a newly installed server. The documented configuration specifies using an IP address of 10.20.10.15 and a default gateway of 10.20.10.254. Which of the following subnet masks would be appropriate for this setup?

A. 255.255.255.0
B. 255.255.255.128
C. 255.255.255.240
D. 255.255.255.254