IFHXRXQT

Hi I am preparing for Saleforce Developer certification (PD-01) , I came acroos the below question.

A developer wants multiple test classes to use the same set of test data?

As per my kowledge , answer should be 'create set up method for each test class'

But in dump paper, it says,  "use seealldata==true annotaton in the test class"

i am not getting how it works, please explain.

Also please share dumps if u have

No matter what i do, i can not get this to work in my DE org.  I've tried reinstalling the package as well, still will not work.
Any suggestions?  Anybody?