In JavaScript, arrays are reference types. A direct assignment (let arr2 = arr1;) creates a new variable arr2 that points to the same memory location as arr1, not a new array. To create a true copy, a method that returns a new array instance must be used.

The slice() method extracts a portion of an array and returns a new, shallow-copied array object. Similarly, Array.from() creates a new, shallow-copied Array instance from an iterable object like an array. Both methods result in arr2 being a distinct array in memory, independent of arr1.

C. Let arr2 = arr1;

This line creates a reference. The variable arr2 will point to the exact same array object as arr1, not a new one.

D. Let arr2 = arr1.sort();

The sort() method modifies the array in-place and returns a reference to that same, now-sorted, original array.

1. Mozilla Developer Network (MDN) Web Docs

Array.prototype.slice(): "The slice() method returns a shallow copy of a portion of an array into a new array object selected from start to end (end not included) where start and end represent the index of items in that array. The original array will not be modified." (Section: "Return value").

2. Mozilla Developer Network (MDN) Web Docs

Array.from(): "The Array.from() static method creates a new

shallow-copied Array instance from an iterable or array-like object." (Section: "Description").

3. Mozilla Developer Network (MDN) Web Docs

Array.prototype.sort(): "The sort() method sorts the elements of an array in place and returns the reference to the same array

now sorted. The default sort order is ascending..." (Section: "Return value").

4. Eloquent JavaScript

3rd Edition by Marijn Haverbeke (a resource used in many university curricula): "Objects and arrays

on the other hand

are stored differently... When you copy a variable that holds an object

you are copying the reference to that object

not the object itself... If you want to create a new array with the same elements

you can use the slice method with no arguments." (Chapter 4: Data Structures: Objects and Arrays

Section: "Objects and arrays are mutable").