Explanation:

Scalability refers to a system's ability to handle a growing amount of work or to be easily enlarged to accommodate that growth. If a network can easily add additional users, it means it is scalable, as it can expand its capacity to serve more participants without significant redesign or performance degradation. Option (1) 'secure' relates to protection, not expansion. Option (2) 'dedicated' implies exclusive allocation, not ease of adding users. Option (3) 'decentralized' refers to distributed control, not directly to user expansion capability.