On that basis, place the following four words in the four empty cells in the grid so that each word is directly below a word that has the same variant of the unknown property:
ASPECT EFFECT REJECT SELECTThere are 4! (=24) ways in which these four words can be arranged, only one of which is correct. The fact that both groups of four words are in alphabetical order is not relevant to the solution of this puzzle, although the order in which the words in the top row of the grid has been arranged is significant.