阅读理解

     One day an Australian farmer Joe saw a bright light in the sky. The light came nearer and nearer and suddenly Joe saw that it was a spaceship. The spaceship landed in the field quickly.

    The door of the spaceship opened and two strange beings (怪物) climbed out. They seemed to be half man and half bird. Joe was afraid of them. He tried to run away. But the spacemen walked towards him, picked him up and carried him into the spaceship. They put wires (电线) from a machine onto his head and then they were able to speak to him in English.

    They asked him questions about the Earth. "We're from Venus (金星)," they said. "But it is getting very hot there. A lot of our people are dying and we haven't much time left. We are trying to find a new home. "

     After some time they freed (释放) Joe and at last the spaceship took off and couldn't be seen.

     Joe told his friends about the spacemen. But no one believed his story. You'll believe me one day," Joe told them. "The spacemen will come back."

根据问题填空：

下列对于铯（Cs）的性质的预测中，正确的是（   ）

泰国大米连续6年稳居世界销量第一，由此赢得“世界米仓”的桂冠。泰国水稻种植的优越区位条件是                                                  （   ）
①平原面积广，土壤肥沃                     ②日照充足，昼夜温差大
③热带季风气候，雨热同期                    ④农业机械化水平高
⑤市场需求大，交通运输方便              ⑥农业劳动力充足

学习了电学知识后，小明、小亮和小慧所在的兴趣小组发现：电学量的变化往往能够用来反映力学、热学、光学等物理量的变化。在老师的点拨下，他们在探究过程中不断完善和优化方案，共同设计了一种用电学量的变化来反映力学量——距离变化的装置。

如图所示是他们最初设计的装置原理图。图中R₀是定值电阻，ab是沿竖直方向固定放置的金属杆，其总电阻为9Ω，长60cm，粗细均匀，电阻随长度均匀变化。M是上下均有挂环、可沿竖直导轨上下移动的小物块，M上连有一根左端有滑片P、电阻不计的水平金属细杆，细杆、导线及P与ab均接触良好，P在ab的中点时，对应于肘既不上移也不下移的位置。

除金属杆ab、小物块M、金属细杆和导轨外，他们还准备了以下器材：

A.电源（提供4 V的稳定电压）

B.电流表A（量程0—0.6 A）

C.电压表V₁（量程0～3 V）

D.电压表V₂（量程0～15V）

E.定值电阻R₀（1Ω、3Ω、5Ω和6Ω的电阻各一个）

F.开关S一个，导线（足够长）若干