Which test to run when using android studio for unit testing

I am working through an android app tutorial course on udacity.com. I have come to a lesson where it's introducing testing. However, the video for the current class is showing how to run a test where only one run test option is available. seen here: http://ift.tt/1cbqklw

but my android studio shows a number of options

and I am not sure what is the correct one to use, or even what the differences between them are. Could anyone shed some light on why I have the 4 different choices and what they are? In particular the first and second options are confusing me. the third and fourth options are intuitive enough to understand.

Thank you.