Which word contains two phonemes?

To determine which word contains two phonemes, it's important to understand what a phoneme is: it is the smallest unit of sound in a language that can distinguish one word from another.

In the case of the word "bee," it consists of two distinct sounds: /b/ and /iː/. The /b/ represents the initial consonant sound, while /iː/ represents the vowel sound. Together, they form two phonemes, making this the correct answer.

In contrast, the other words contain more or fewer phonemes when analyzed. "Plan" has four phonemes (/p/, /l/, /æ/, /n/), "eaten" has four phonemes as well (/iː/, /t/, /ə/, /n/), and "dust" consists of four phonemes (/d/, /ʌ/, /s/, /t/). Therefore, "bee" stands out as the word with exactly two phonemes.