To answer this question, we need to understand the conditional (ternary) operator in Java.
The conditional operator (?:) has the following syntax:
(condition) ? expression1 : expression2
If the condition is true, expression1 is evaluated and becomes the result of the entire expression. If the condition is false, expression2 is evaluated and becomes the result.
In the given code snippet:
String first = (elements.length > 0) ? elements[0] : null;
The condition is "elements.length > 0", which checks if the length of the array "elements" is greater than 0.
If the condition is true (i.e., the array has at least one element), the expression "elements[0]" is evaluated and assigned to the variable "first". So, the variable "first" is set to the value of the first element in the array.
If the condition is false (i.e., the array is empty), the expression "null" is evaluated and assigned to the variable "first". So, the variable "first" is set to null.
Therefore, the correct answer is:
D. The variable first is set to elements[0].