C#.NET indexers — Student must support two-dimensional indexing as in: Student s = new Student(); s[1, 2] = 35; Which declaration enables this write-only indexer?

Introduction / Context:
C# indexers can accept multiple parameters, enabling two-dimensional indexing syntax like s[i, j]. To make only assignments possible (write-only), the indexer should expose only a set accessor and omit a get accessor.

Given Data / Assumptions:

• Student uses an internal 2D int array (int[,]) for storage.
• Goal: support s[1, 2] = 35; (write-only indexer).
• We use correct C# keywords and syntax.

Concept / Approach:
A valid two-parameter indexer has the form public int this[int i, int j] { set { a[i, j] = value; } }. The indexer’s declared type (int) is the value being assigned. No get accessor means reads like var x = s[1,2]; are disallowed.

Step-by-Step Solution:

Verification / Alternative check:
Compile the declaration and test with the given assignment; it compiles. Attempting to read s[1,2] will fail, as intended.

Why Other Options Are Wrong:

• A/B: Use VB-style keywords and, in A, the backing array type is wrong (int[] with 2D size).
• D: Invalid indexer signature; missing parameters in the indexer declaration.

Common Pitfalls:
Confusing jagged arrays with rectangular arrays and mixing language keywords from VB into C#.

Final Answer:
class Student { int[,] a = new int[5, 5]; public int this[int i, int j] { set { a[i, j] = value; } } }