Choice "C" is correct. In a large multinational organization (or even a medium sized national organization), managing remote access would be the responsibility of a network administrator. The question used the qualifiers "large" and "multinational" to distinguish this organization from that of a small organization, where many different job functions might be combined in a single individual. In a large organization, a network administrator would not perform any of these other functions (even assuming that the network administrator had the skillset to perform them). IT jobs often require a very specific skillset.
Choice "d" is incorrect. A network administrator would not develop application programs.
Choice "b" is incorrect. A network administrator would not review security policy.
Choice "a" is incorrect. A network administrator would not install operating system upgrades. Few network administrators would have the knowledge and/or training to install operating system upgrades other than possibly simple PC desktop operating systems.