已知扇形的圆心角为$\frac{\mathrm{\pi }}{3}$，半径为3，则扇形的弧长l=____ 

建立与统治：____年，内迁的____人灭掉西晋。镇守长江下游的皇族____于____年重建晋王朝，以____为都，史称____。司马睿当皇帝，得益于____为首的南北大贵族的拥戴，时人称之为“____”。东晋成功抵御了来自北方的军事威胁，统治局面相对稳定，江南出现了“____，____”的景象。

灭亡：东晋末年，政权落入武将手中。____年，东晋灭亡。

某腐蚀印刷电路板的废液中含有CuCl₂和FeCl₂，为了分析该废液的组成，取1000g废液，设计如下实验方案进行探究：

实验过程中加入废铁屑的质量、析出Cu的质量的数据记录如下表：

（注：废铁屑中的杂质不溶于废液也不与废液反应，不考虑过滤中的损失。）

铜及其化合物在生活、生产中有广泛应用．请回答下列问题：

（1）自然界地表层原生铜的硫化物经氧化、淋滤作用后变成CuSO₄溶液向地下深层渗透，遇到难溶的ZnS，慢慢转变为铜蓝（CuS）．写出CuSO₄转变为铜蓝的离子方程式　____ 。

（2）工业上以黄铜矿CuFeS₂）为原料，采用火法熔炼工艺生产铜的中间过程会发生反应：2Cu₂O+Cu₂S6Cu+SO₂↑，该反应的氧化剂是　____ ；验证反应产生的气体是SO₂的方法是____。

（3）图I是一种新型燃料电池，它以CO为燃料，一定比例的Li₂CO₃和Na₂CO₃熔融混合物为电解质，图II是粗铜精炼的装置图，假若用燃料电池为电源进行粗铜的精炼实验．

①写出A极的电极反应式　____ 。

②要用燃料电池为电源进行粗铜的精炼实验，粗铜板应与____ 极（填“A”或“B”）相连；若粗铜中还含有Au、Ag、Fe，它们在电解槽中的存在形式和位置为　____ 。

③当消耗标准状况下1.12LCO时，精铜电极的质量变化情况为____ 。

（4）现向一含有Ca²⁺、Cu²⁺的混合溶液中滴加Na₂CO₃溶液，若首先生成CuCO₃沉淀，根据该实验可得出的结论是　____ （填序号）

A．Ksp（CuCO₃）＜Ksp（CaCO₃） B．c（Cu²⁺）＜c（Ca²⁺）

C．＞D．＜．

阅读理解

    The Leaning Tower of Pisa was straight like a pole when the construction began in 1173. It started to shift direction soon after construction because of poor foundation in addition to the loose layer of subsoil(底土). At the beginning, it leaned to the southeast before the shaky foundation started to shift leaning towards the southwest. After the period of structural strengthening at the beginning of the 21^st century, now the Leaning Tower of Pisa leans at an angle of 3.97 degrees.

    In 1178, the shift in direction was observed for the first time when the construction had progressed further to the third floor. The tower was heavy for the three-meter foundation that was built on a weak area of land.

    For compensating(补偿) the leaning position, the builders started to construct the upper floors with one side higher than the other one. This caused the tower to lean in the other direction. This unusual structure led to the tower being actually curved. In spite of these efforts, the tower kept on leaning.

    The government of Italy started to plan prevention of the complete collapse of the tower in 1964. However, a request was put forward by the authorities to keep the leaning position because of the tourism industry of the region.

    After nearly two decades of careful planning by engineers, historians and mathematicians, the stabilization efforts for the Leaning Tower of Pisa started in 1990. The tower was closed for the general public and the people living nearby moved away. For reducing the total weight of the tower, its seven bells which represented the seven musical notes were removed. The tower was reopened for the general public on December 15, 2001.

    In May 2008, after removing another 70 metric tons of earth, the engineers announced that the tower had been finally stabilized and it would remain stable for at least 200 years.