$15-$ It extends a private network $($intranet$)$ across a public network Internet$)$ and enables users to send and receive data across shared or public networks as if their computing devices were directly connected to the private network. Applications running benefit from the functionality, security, and management of the private network while taking advantage of the flexibility of the Internet. Find the missing word

a$-$ Private Internet

b$-$ Private Extranet

c$-$ Virtual Private Network $($VPN$)$

d$-$ private network