Your browsing the internet and realize your browser is not responding which of the following will allow you to immediately exit a program without rebooting the computer

Hey there! Hello!

This really depends on what operating system and version of that system you're running (or the question you have is referring to). Here's two answers, use whichever one seems more relevant. (If the question doesn't specify what operating system it's referring to, I'd suggest the Windows answer – it tends to be a little more universal than OS X/macOS). 

For Windows, the best and most universal way to do it for pretty much every version I can think of is to do ctrl+alt+delete and select Task Manager from the menu or screen that pops up. This will usually only work if you only have an application that has stopped working and your computer itself is not frozen. From there, you can select the browser in question (for example, Google Chrome, Firefox, Safari, etc.) and end the task. 

For OS X/MacOS, you can go to the Apple logo in the top left corner of the menu bar and select Force Quit from the dropdown menu. This'll give you a small box of all of the current open applications where you can select the browser in question and select "Force Quit." You can also just type command+option+esc if you're into shortcuts. 

Hope this helped you out! Feel free to ask me any additional questions if you have any. :-)