（1）地壳中含量最多的金属元素是____．

（2）生活中的钢铁制品通常是铁的合金，合金属于____ （填“混合物”或“纯净物”）．

（3）一般的导线由铜丝组成，说明铜有其良好的____性（填一条）．

（4）早在西汉时期，人们主要采用“湿法冶金”．如将铁浸入硫酸铜溶液中，该反应的化学方程式为____ ，基本反应类型为____ ．

学校是我们幸福____和____的地方。

①金属镁在空气中比铝更易点燃，说明镁比铝活动性强；

②金属铝比金属锌更耐腐蚀，说明锌比铝活动性强；

③硫酸铜、石灰水配制农药波尔多液，不宜用铁制容器；

④金属锌与稀硫酸反应速率适中，更适于实验室制取氢气．

Big ocean(海洋)fish have almost disappeared from the world since the start of business fishing in the 1950’s．The scientists found that the number of large fish has dropped by 90 percent in the past fifty years．The study took ten years．The researchers collected records from fishing business and governments around the world．The magazine Nature published the findings．
The scientists say the common way called longline fishing is especially harmful to large fish．This way includes many fishing lines that are connected to one boat．If these lines are joined together，they can reach one hundred kilometers．They hold thousands of sharp metal hooks to catch fish．Longline fishing is especially common in the Japanese fishing industry．Records show that Japanese boats used to catch about ten fish for every hundred hooks．The study says longline fishing boats now might catch one fish per hundred hooks．
The scientists say business fishing can destroy groups of fish much faster than in the past．The study suggests that large fish can disappear almost completely from new fishing areas within ten to fifteen years．Ocean life system could be destroyed．
It’s not the only worry that the number of large fish is becoming smaller and smaller．What’s worse．they are smaller in size than their ancestors(祖先)．