已知关于x的一元二次方程x2-mx-2=0.
My father never __________.
选择合适的选项完成对话。
Cheng Jie: Good morning!
Amy: ____
Cheng Jie:Nice to meet you.
Cheng Jie: ____
Amy: My name is Amy.
Cheng Jie:____
Amy: I'm from the USA.
A. Where are you from ? B. Nice to meet you, too.
C. What's your name? D. Good morning.
传染病的特点是( )
①求金属块A受到的浮力F浮
②求水对容器底部的压力F水
③现将绳子剪断,求绳子剪断后容器对水平地面压强变化了△P