Choose the missing term out of the given alternatives

C4X, F9U, I16R, ?

The sequence is: C4X, F9U, I16R, ?

Analyzing the first letter pattern:

C = 3rd letter of alphabet

F = 6th letter of alphabet

I = 9th letter of alphabet

The position increases by 3 each time: 3, 6, 9, 12

The 12th letter is L

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Analyzing the number pattern:

4 = $2^2$

9 = $3^2$

16 = $4^2$

The next term is $5^2 = 25$

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Analyzing the last letter pattern:

X = 24th letter of alphabet

U = 21st letter of alphabet

R = 18th letter of alphabet

The position decreases by 3 each time: 24, 21, 18, 15

The 15th letter is O

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Combining all patterns:

First letter: L

Number: 25

Last letter: O

Therefore, the missing term is L25O.

The answer is Option 4: L25O