首页 > 英语四级
题目内容 (请给出正确答案)
[主观题]

Copper(铜)was the first metal that man learned to make.In some mountainous lands ther

Copper(铜)was the first metal that man learned to make.In some mountainous lands ther

e were rocks streaked with green minerals.One day some rocks were accidentally heated by a roaring fire.When the fire burned low,little beads of copper were seen on the rock wall.After that,men heated the rock deliberately to see whether more copper would appear.They soon found a good way to make copper.They would build a trench on a hillside and fill it with charcoal and copper-bearing rock.They covered this furnace with flat stones.They started a wood fire to heat the charcoal and the hot charcoal released copper from the rock.A hot red pool of melted metal formed at the mouth of the trench.When it was cool,the solid metal could be lifted out and cut and pounded into shapes.

The first copper was probably made by()

A、experimenting

B、accident

C、someone deliberately building a fire

D、someone who knew that there was copper in the rock

查看答案
答案
收藏
如果结果不匹配,请 联系老师 获取答案
您可能会需要:
您的账号:,可能还需要:
您的账号:
发送账号密码至手机
发送
安装优题宝APP,拍照搜题省时又省心!
更多“Copper(铜)was the first metal t…”相关的问题
第1题
Bronze is ____ of copper and tin.

A.composed

B.coined

C.consisted

D.involved

点击查看答案
第2题
A.90% copper and 10% silver.B.90% silver and 10% copper.C.90% silver, 9% copper, and 1

A.90% copper and 10% silver.

B.90% silver and 10% copper.

C.90% silver, 9% copper, and 1% lead.

D.None of these.

点击查看答案
第3题
A.An alloy of copper and silver.B.Pure silver or pure gold.C.An alloy of copper and fi

A.An alloy of copper and silver.

B.Pure silver or pure gold.

C.An alloy of copper and fin.

D.An alloy of gold and silver.

点击查看答案
第4题
Silver is the best conductor of electricity, copper ________ it closely.A) followed

Silver is the best conductor of electricity, copper ________ it closely.

A) followed

B) following

C) to follow

D) being followed

点击查看答案
第5题
2005年,在英国上线的全球首家P2P网络借贷平台是()。

A.Zopa

B.Apple

C.Copper

D.Nober

点击查看答案
第6题
某3阶FIR滤波器的系统函数H1(z)为(1)试确定幅度响应和H1(z)相同的所有FIR沸波器的系统函
某3阶FIR滤波器的系统函数H1(z)为(1)试确定幅度响应和H1(z)相同的所有FIR沸波器的系统函

某3阶FIR滤波器的系统函数H1(z)为

(1)试确定幅度响应和H1(z)相同的所有FIR沸波器的系统函数。

(2)上述FIR滤波器邸个是最大相位系统,哪个是最小相位系统?

点击查看答案
第7题
我国的马歇尔K值大约是美国的两倍左右,而FIR约为美国的一半。()
点击查看答案
第8题
FIR单位脉冲h(n)是有限长。()
点击查看答案
第9题
已知FIR数字滤波器的系统函数为试分别画出其直接型、级联型结构。

已知FIR数字滤波器的系统函数为

试分别画出其直接型、级联型结构。

点击查看答案
第10题
FIR数字滤波器结构中,无反馈运算,运算误差小。()
FIR数字滤波器结构中,无反馈运算,运算误差小。()

点击查看答案
退出 登录/注册
发送账号至手机
密码将被重置
获取验证码
发送
温馨提示
该问题答案仅针对搜题卡用户开放,请点击购买搜题卡。
马上购买搜题卡
我已购买搜题卡, 登录账号 继续查看答案
重置密码
确认修改