You have received a complaint from DevOps that their hosted application is being blocked from establishing the connection with the database. The application is hosted at $10\mathrm{.}213\mathrm{.}15\mathrm{.}11/24$ and the sql server is $10\mathrm{.}213\mathrm{.}15\mathrm{.}121/24.$ The developers used IP addresses instead of domain names. Which of the following could be the reason of issue?

A$)$ incorrect gateway configuration on any of the hosts

b$)$ incorrect DNS configuration on any of the hosts

C$)$ incorrect L$2$ switch configuration

d$)$ incorrect settings on the NGFW that is right after gateway