Go to the site version for smartphones.
17. Which letter should replace the question mark?
  IQ test. Fast and free online iq test # 3 with answers and solutions. Question # 17. Which letter should replace the question mark?
 

Explanation:
The alphabetic number of the next letter is multiplied by 2 (from left to right). In terms of the alphabetic order of letters. F × 2 = L; L × 2 = X.