发票应当由谁开具？
参考答案：
销售商品提供服务时，收款方向付款方开票；收购物资时，付款方向收款方开票。
根据汉语提示写出单词。（5分）
小题1:Dad, could you bring me some drinks and ________(小吃、小食品)?
小题2:There are ________(五十) teachers in our school.
小题3:How did you get your ___________ (兼职的) job?
小题4:I need to _________(完成) my homework first before going out.
小题5:Don’t ___________ (担心). I can help you with your chemistry.
三七的性状？海马的性状？
