The correct Active/Passive form of the given sentence is:

☀ Sweety was promised a new doll on her birthday.

Explanation for other options:

☀ Sweety had been promised a new doll on her birthday. This option uses the past perfect tense ("had been promised"), which suggests an action completed before a certain point in the past. The original sentence is in the simple past tense, so the correct form should be "Sweety was promised a new doll on her birthday."

☀ Sweety were promising a new doll on her birthday. This option uses "were promising," which is in the active voice and does not represent the correct passive form. The correct form should use the passive construction "was promised."

☀ Sweety was promising a new doll on her birthday. This option uses "was promising," which is in the active voice and does not represent the correct passive form. The correct form should use the passive construction "was promised."