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no one seems interested in this one have tried to delete

In each case it would depend on what exactly the position is on the board. Anyway, in most cases it would usually be:

I. Queen if there are lots of other pieces on the board, 2 rooks if there are not many other pieces left

II. 3 pawns in an endgame, knight otherwise

III. 3 pawns in an endgame, bishop otherwise

IV. Knight + bishop

V. Good idea if it leads to a mate or forced win of material, otherwise there are probably better things your knight/bishop could be doing

Actually, I'd prefer 3 pawns to a knight, because there is a good chance that by moving them so that they protect each other, you'll get a queen out of it!