What will mylist[3:] return?

The operation mylist[3:] in Python utilizes slicing, which allows you to extract a portion of a list based on specified indices. When you use the syntax [start:end], it retrieves elements starting from the index defined by start up to, but not including, the index defined by end. In this case, since no end index is specified (indicated by the absence of a value after the colon), Python assumes it extends all the way to the end of the list.

Therefore, mylist[3:] will return a new list containing all elements from the fourth element onward (since list indexing starts at 0). This means it includes the element at index 3 and every subsequent element until the end of the list, which aligns perfectly with the correct answer.

Understanding this concept is crucial as list slicing is a fundamental operation in Python that enables developers to manipulate and work with subsets of data efficiently.