Multiple choice technology programming languages

What is the .NET collection class that allows an element to be accessed using a unique key?

  1. HashTable

  2. ArrayList

  3. SortedList

  4. All of above

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A Correct answer
Explanation

HashTable (and its generic version Dictionary) is designed specifically for key-value access where each key must be unique. ArrayList and SortedList store elements without requiring unique keys - ArrayList is a dynamic array and SortedList maintains sorted order but allows duplicates.