You're quite right. The point here is that they have translated
'ein weißes Salz' as 'white salt', not 'A white salt'.
I'm happy for them to talk about A white salt, but the German and the English need to match.
You guys have been grumbling about this for two years now, and it's still not fixed. Can I encourage you all to give the Owl feedback so we can get this (and all the other little niggles in this course) straightened out?
Have a sunshine day. :)