What statements are correct about the birthday party? 下面哪些是关于生日聚会正确的说法？
选项：

A:A birthday party is a celebration of someone's birthday.;
B:A birthday cake is usually served with lit candles.;
C:The candles are to be blown out after a "birthday wish" has been made.;
D:The song Merry Christmas is sung by the guests.