Choose the odd one out.

The answer is B. ABA.

All the other options are three-letter sequences that contain two different vowels. In ABA, the two vowels are A.

A three-letter sequence is a string of three letters. A vowel is a letter that represents a sound produced by the vocal cords with relatively open vocal tract.

The following are three-letter sequences that contain two different vowels:

• OTP
• SZX
• UVB
• YQR

In OTP, the two vowels are O and T.

In SZX, the two vowels are S and X.

In UVB, the two vowels are U and V.

In YQR, the two vowels are Y and Q.