I thought so, but I was thrown for a loop by dxb's "all mixed up between different lines" (I thought of troy presented a "set" which were independent of each other)... ~ tsuwm

Yeah, now I look more closely, you're right. I jumped to the wrong conclusion. Still, mixing up the lines adds to the interest...perhaps.

And they're not difficult.

Edit:

After a PM from WW, I realise that it is evidently more difficult than I thought it would be. What I’ve done is what I thought she had done.

- I have made 7 sets of 4.

- In each of the 7 sets there is one item which, if removed, leaves a different set of 3, call it a sub-set, that the fourth (removed one) would not fit into.

- Then I’ve mixed them all up.

Hope that helps – I seem to have been too obscure for my own good – anyway, I didn’t explain it well enough. I don’t think I mentioned the sub-sets. Oh dear, I’m sorry about that.

The sets and sub-sets (with the sub-sets in brackets) are:

jewellery materials, (precious metals)

loaves, (towns)

body parts, (measures)

rivers, (colours)

papers, (vegetable products)

cats, (countries – sort of)

boats, (activities)