In C#, how can I pick between two items?

In C#, how can I pick between two items?

This may have been asked before, but if it has I can't find it. I'm
writing a small game where sums are randomly generated for the user to
answer, and correct + incorrect answers are counted. It works thus far,
but I wish to implement a system where the game randomly picks between +,
-, / and * symbols between the two randomly picked numbers and then,
depending on which was picked, changes the way the correct answer is
calculated. For a better idea, here is my current relevant code:
public void makeNewSum()
{
var randomNum = new Random();
num1 = randomNum.Next(0, 10);
num2 = randomNum.Next(0, 10);
answer = num1 + num2;
label1.Text = num1.ToString() + " + " + num2.ToString() + " = ";
txtAnswer.Text = "";
txtAnswer.Focus();
The item 'label1' is where the sum that must be answered is displayed,
though you can probably tell. What I'm trying to figure out is how I can
tell it to choose between " + ", " - ", " / " and " * " where it currently
always says " + ", and then change the variable 'answer' to reflect the
symbol chosen. I was planning to use if statements to reflect the choice
of symbol, but I'm lost for how to have it choose between them in the
first place. Help is greatly appreciated!