दही अच्छी होती है (Dahi achchhi hoti hai)
Here's why:
* Dahi is feminine in Hindi.
* Acchhi (good) is the feminine form of the adjective.
* Hoti hai is the correct conjugation of the verb "to be" in the present tense for the feminine singular.
Therefore, the correct sentence is "Dahi achchhi hoti hai" meaning "Yogurt is good."
The sentence "b acha HOTA hai" is grammatically incorrect because it uses the masculine form of the adjective "acha" and the masculine conjugation of the verb "hota hai" with the feminine noun "b".