用所给词的适当形式填空。
1.There are a lot of children at ________(Ben) party.
2.There ________(be) a big birthday cake on the table.
3.Can you ________(pick) up for me?
4.Look! The children ________(swim) in the river.
5.My sister always ________(have) a birthday party on ________(she) birthday.
6.Our classroom is on the ________(three) floor.
7.The ________(thirteen) number is 9.