Answer: Availability heuristic
Explanation:
Availability heuristic is defined as the shortcut feature that is used by mind which relates with the instant examples while addressing and evaluating any particular situation, event or act. Situation that are concerned with the likelihood of anything occurs in mind immediately with similar example.
According to the situation in question, Frank's situation is depicted with the availability heuristic. Occurrence of "k" letter in beginning is more as compared to the third place is stated by Frank because he is making decision based on the immediate example of number of words that might have occurred in his mind starting with "k" letter as compared to "k" placed at third position.