Which of the following option is used when working with complicated expressions in C++ ?

The question seems incomplete as there are no options provided. However, when working with complicated expressions in C++, you might want to use parentheses to control the order of operations, or use functions to break down the expression into smaller, more manageable parts. You might also use variables to store intermediate results.

The option used when working with complicated expressions in C++ is the use of parentheses. Parentheses are used to group expressions and to dictate the order in which operations are performed. This is especially important in complicated expressions where the order of operations matters.

Here's a step-by-step guide on how to use parentheses in C++:

1. Identify the part of the expression that needs to be evaluated first. This could be a multiplication, division, or any other operation that should be performed before others.

2. Enclose this part of the expression in parentheses. For example, if you have the expression a + b * c and you want to perform the addition before the multiplication, you would write it as (a + b) * c.

3. If there are multiple parts of the expression that need to be evaluated at the same time, you can use multiple sets of parentheses. For example, (a + b) * (c - d).

4. Remember that operations within parentheses are performed before those outside. If there are several sets of parentheses, the operations are performed from the innermost set outwards.

5. Also, remember that if parentheses are not used, the operations are performed according to the precedence rules of C++. Multiplication and division are performed before addition and subtraction.

6. Finally, test your expression to make sure it's working as expected. You can do this by substitifying values for the variables and calculating the result.