B. Before the picnic Mary ... 1) planned her party. 2) made a list of songs. 3) bought cakes. 4) prepared everything alone without help.

Ответ:

• 1) planned her party.

Пояснение:

В тексте сказано: «Mary spent several days carefully planning the event, making a detailed list of food, games, and decorations». Это указывает на то, что она планировала вечеринку заранее.