Which of the following represents a static declaration in C#?

The correct answer indicates a static declaration in C# by utilizing the readonly modifier in tandem with initializing a specific type of array. In the context of C#, the readonly keyword ensures that, once assigned, the reference to the data remains constant, thus preventing it from being modified later.

In this case, the declaration reveals the intention to create an array of Contact objects with a size of 100. This form of declaration signifies that while the contents of the array can be altered, the reference to the array itself cannot be changed after it has been initialized. This is particularly useful in scenarios where you want to ensure data integrity and prevent accidental reassignment, which is fundamental for maintaining robustness in program design.

While other options may represent various forms of array declarations, they do not demonstrate the same level of emphasis on immutability in reference as they lack the readonly keyword or are improperly constructed. For instance, using new Contact[] without specifying the size leaves the array undefined in context, demonstrating a lack of clarity regarding its use in static declaration terms. Therefore, recognizing the correct attributes of the chosen answer contributes to a deeper understanding of static declarations and how they are implemented in C#.