Explanation
A database is a collection of data that is organized and stored in a way that allows easy access, manipulation, and analysis. A database would be the best option for storing information for an application that needs to be accessed by concurrent users and store company information securely. A database can handle multiple user requests, enforce data integrity and security, and perform complex queries and operations on the data. A word processing document, a flat file, and a spreadsheet are not options that can support concurrent users, store company information securely, or perform complex operations on the data. References: CompTIA IT Fundamentals+ Study Guide: Exam FC0-U61, Second Edition, Chapter 5: Database Fundamentals, page 191.