Hello!
The answer is 1.) Click in the side panel
Why?
All of the three other options are correct steps to save a presentation.
2.) Click on the save icon: Clicking on the save icon will show you the saving options that you may use like: saving locations, saving file names, selecting the format and version of the file you want to save, among others.
3.) Giving it a name that makes sense: Giving a name that makes sense will help you to find the file in the future with no effort, you can select the name you want to use after you click on the save icon.
4.) Select save from the file menu: It will be the last step after you have set all your preferences. After this step, you will be able to find the file that you just saved in the location that you have chosen.
Have a nice day!