2000万人口的秦朝，可以调动40万劳动力去修长城，70万人去修秦始皇陵，70万人去修阿房宫，50万人去戍五岭……这是西周天子难以办到的事。其直接原因在于秦朝与西周的（   ）

B

    Today is Sunday. Mike and Peter 1 go to school. Listen! They are talking about the life 2 in the room.

    "3 will the world be like" asks Peter. "I think that the world will be a 4 place to live in. And we will 5 machines and robots at home. They will help us do lots of 6." says Mike.

    "The robots will help 7 cook dinner, clean the houses and 8 the old people. I think there will 9 a kind of medicine (药) and it can make me 10 more than 100 years ," Peter says.

    "What will you do then?" asks Mike.

    "Then I will take my great – grandchildren to the moon," says Peter. "The moon? I will go to the Mars (火星) with my wife ," says Mike.

已知命题：
p₁：函数$f\left(x\right)=x+\frac{1}{x-1}\left(x>1\right)$的最小值为3；
p₂：不等式$\frac{1}{x}>1$的解集是{x|x<1};
p₃：$\exists \alpha ,\beta \in R$ ，使得$\sin \left(\alpha +\beta \right)=\sin \alpha +\sin \beta$成立;
p₄：$\forall \alpha ,\beta \in R$，$\tan \left(\alpha +\beta \right)=\frac{\tan \alpha +\tan \beta }{1-\tan \alpha \tan \beta }$成立.
其中的真命题是(   )

在实验室可用如图装置制取蒸馏水，回答下列问题．