根据短文内容, 补全下列句子。

David wants to buy a Christmas present for his mother. David's father gives him $5 a week and David puts $2 it his bank account （账户）every week. After three months David takes $20 out of his bank account and goes to the shop. He looks for a great present He sees a beautiful brooch （胸针）in the shape of his favourite pet. He says to himself, "My mother loves jewellery （珠宝）, and the brooch costs only $17."He buys the brooch and takes it home. He wraps （裹） the present in Christmas paper and then puts it under the tree. He is very happy and he wants to see the joy （喜悦）on his mother's face that day. When his mother opens the present, she screams （尖叫）.She sees a spider （蜘蛛）