______ ciphers leave letters in their original positions.

• A. Transposition
• B. Substitution
• C. Both A and B
• D. Neither A nor B

Answer: (B)

Understanding how these two cipher types treat the positions of letters is the key. A substitution cipher replaces each plaintext letter with another letter according to a mapping, so the sequence length stays the same and each position remains in its place—the first character is still the first position, only its symbol has changed. In this way, letters stay in their original spots, even though they’re different letters.

A transposition cipher, on the other hand, moves letters around according to a rule or key. The order changes, so the letters no longer occupy the same positions as in the plaintext.

So the statement describes substitution ciphers, making substitution the correct choice. The other options don’t fit because a transposition cipher alters positions, and a combination like “both” or “neither” would misstate whether letters can stay in their original positions.