Odd-One Out: GH24

Explanation:
To determine the odd-one out among the given terms, we need to analyze the pattern or rule that governs the sequence of each term.

- EF22: The first letter, E, is followed by the letter F, which is one letter ahead in the English alphabet. The number 22 represents the sum of the positions of the letters E and F in the alphabet (5 + 6 = 11). Therefore, the rule for this term is that the next letter is one position ahead, and the number represents the sum of the positions of the two letters in the alphabet.

- JK42: The first letter, J, is followed by the letter K, which is one letter ahead. The number 42 represents the sum of the positions of the letters J and K in the alphabet (10 + 11 = 21). Therefore, the rule for this term is the same as the previous one.

- GH24: The first letter, G, is followed by the letter H, which is one letter ahead. However, the number 24 does not represent the sum of the positions of the letters G and H in the alphabet (7 + 8 = 15). This breaks the pattern established by the previous terms.

- VW90: The first letter, V, is followed by the letter W, which is one letter ahead. The number 90 does not represent the sum of the positions of the letters V and W in the alphabet (22 + 23 = 45). Again, this term does not follow the pattern established by the first two terms.

- IJ38: The first letter, I, is followed by the letter J, which is one letter ahead. The number 38 represents the sum of the positions of the letters I and J in the alphabet (9 + 10 = 19). This term follows the pattern established by the first two terms.

Based on the analysis above, GH24 is the odd-one out among the given terms since it does not follow the pattern of the other terms.