Explanation:

- Option 1: AdCb

- This is a mix of uppercase and lowercase letters in alternating positions.

- Option 2: YxYw

- This option has uppercase letters all at the start, followed by lowercase letters. The pattern is not alternating, unlike others.

- Correct answer

- Option 3: MpOn

- Alternates between uppercase and lowercase letters similar to option 1.

- Option 4: SvUt

- Fits the alternating pattern seen in options 1 and 3.