which file in the raster stack do I use?

I have a *.zip file from arcmap. It contains a bunch of files. In the top directory, one *.xml, one *.ovr, and two nested directories, *.dat and *.nit files (in one), and 6 *.adf files (in the other).

I drag the *.zip into qgis and there it sits in the layers box as a stack of 6 rasters (see picture).

My big bad question is: If I want to perform raster calculations on this, or clip the raster, or warp it, or any other such thing, which file/layer do I choose, and why?

the answer is: one of the files in the directory with the spatial files is the biggest file. That's the one to drag into qgis and manipulate.