中国古代四大发明是中国古代科技的里程碑。中国四大发明中，技术雏形最早的是

反证法证明的关键是在正确的假设下得出矛盾,这个矛盾可以是(    )

①与已知矛盾；②与假设矛盾；③与定义、定理、公理、法则矛盾；④与事实矛盾

____ We had a lot of fun _______ (sing) in the classroom.
____ She decided ________ (buy) the red dress.
____ This sound made the baby ________ (cry).
____ Most boys enjoy _______ (play) football after school.
____ The shop is always ______ (crowd) on weekends.
____  Would you like _____ (go) shopping with me?
____ I saw a little girl ______ (look) for her parents on the street when I walked across it.
____ ______ (be) you at the shop last Friday?
____ The boy spends a lot of time ________ (practice) the piano in the room.
____ Look! Who _______ (stand) near the door?

某商店5天的营业额如下（单位：元）：14845，25706，18957，11672，16330，利用计算器求得这5天的平均营业额是（　　）

下列划线词语意思相同的一项是（    ）