补全对话。

A. Happy birthday! B. I will help you. C. Sorry, mum. I can't. D. Who can help me? E. She's buying things for my birthday party.

Sam: Where's your mum?

Jack: She's at the supermarket.

Sam: Can I come to your birthday party?

Jack: Of course, you can.

Mum: I can't carry the bags.

Jack: I'm making a birthday card.

Sam:

Mum: Thank you, Sam. Oh no, all the balloons are flying away.

Sam: But look at the sky. It says "".