For coding Questions in your Test, from the languages option in your editor, you can change the programming language to write your code. The code editor automatically resets according to the chosen language.
With a coding question, your test setter may intend to assess your skills in specific programming languages. Therefore, the languages option may provide only those languages for you to choose, and this implies that your test setter expects you to write the logic and define the solution using the allowed languages.
Example: In your HackerRank Test, assuming you are at a question which requires to write the logic to find the first non-repeated character in a string. Your test setter may want to assess your coding skills in C# and Python, and hence, the languages option provides only the C# and Python languages to choose from. You must define the coding logic for this question in C# or Python.