Which of the following statements is true about arrays?

The statement that arrays have a fixed size once declared is accurate. In most programming languages, when an array is created, its size must be specified and cannot be changed later. This characteristic is pivotal to how arrays operate: the amount of memory allocated for the array is based on the size defined at the time of declaration. It allows for efficient memory allocation and access, as the data stored in an array can be accessed directly using an index.

This fixed size distinguishes arrays from other data structures like lists or dynamic arrays, which can grow or shrink in size during runtime, providing more flexibility but at the cost of some efficiency. The ability to directly access elements by their index is one of the key benefits of using arrays, making them a fundamental concept in programming and data management.