The index() function in Appian is used to retrieve a value from an array at a specified position. Appian arrays are 1-indexed, meaning the first element is at index 1, the second at index 2, and so on. In the expression index({"a", "b", "c"}, 1, "x"), the function is instructed to retrieve the element at index 1 from the array {"a", "b", "c"}. Since 1 is a valid index for this array, the function returns the first element, which is "a". The third parameter, "x", is a default value that is only returned if the specified index is out of the array's bounds (e.g., 0 or 4).

B: The value "b" is located at index 2, not index 1.

C: The value "c" is located at index 3, not index 1.

D: The default value "x" is only returned when the specified index is out of bounds. Index 1 is a valid position in the given array.

1. Appian Documentation, index() Function: The official documentation specifies the function's syntax as index(array, index, [default]). It explicitly states that the index parameter is 1-based and that the default value is returned only "if the given index is out of bounds." The provided examples, such as index({10, 20, 30}, 2, 0) returning 20, confirm that for a valid index, the element at that position is returned, and the default value is ignored.

Source: Appian Product Documentation, Appian Functions, index().