Cardinality of distinct letters in a word: Find the number of distinct letters in the set {x : x is a letter of the word ASSASSINATION}.

Introduction / Context:
Cardinality here means the count of unique elements. For a word, it is the number of distinct letters ignoring repetition.

Given Data / Assumptions:

• Word: ASSASSINATION

Concept / Approach:
List unique letters present in the word, each counted once in the set.

Step-by-Step Solution:
Distinct letters: A, S, I, N, T, OCount = 6

Verification / Alternative check:
Scan the word left-to-right ensuring no new letters beyond {A,S,I,N,T,O} appear.

Why Other Options Are Wrong:
4 and 2 underestimate; 8 overestimates the unique letters.

Common Pitfalls:
Counting repeated letters multiple times.

Final Answer:
6