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Can I say,

(a) On / At the birthday party, his mother baked a big , tasty cake and lots of delicious food for the birthday party.
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Vincent, please check your sentences and think a moment before posting. There is no point in mentioning 'birthday party' twice in the sentence.

(a) For the birthday party, his mother baked a big, tasty cake and prepared lots of delicious food.
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After I made corrections, Can I say,

(a) On / At the birthday party, his mother baked a big , tasty cake and prepared lots of delicious food.