题干

小明自己制作了一个哨子,如图所示,在筷子上缠一些棉花,做成一个活塞,用水蘸湿棉花后插入两端开口的塑料管.吹管的上端,可以发出悦耳的哨声.这哨声是由 ____产生的.上下推拉活塞,可以改变声音的 ____

上一题 下一题 0.0难度 选择题 更新时间:2018-09-24 08:10:05

答案(点此获取答案解析)

空气柱振动,音调

同类题4

Read the passage and fill in the blanks with the proper words(在短文的空格内填入适当的词,使其内容通顺,每空格限填一词,首字母已给)
    A thousand years ago, Hong Kong was covered by a thick forest. As more and more people came to live in Hong Kong, these trees were cut down and burnt. Now there is no forest left, though there are still some small areas covered with trees. We call these “woods”.
    Elephants, tigers and many o____  animals were living in the thick forest. When people came to live in Hong Kong, the animals began to die out. Early farmers grew rice and r____  pigs and chickens in the valleys. They cut down the trees and burnt them. They needed fire to keep t____  warm in winter, to cook their food and to drive away the dangerous animals. Elephants quickly d____  because there was not enough food for them. So did most of the wolves and tigers.
    You might think that there are no longer any animals in Hong Kong e____  in the zoos, but there are still about 36 different animals living there. One of the most lovely of Hong Kong's animals is the barking deer. There are beautiful little animals w____  a rich brown coat and a white patch under the tail. They look like deer but they are much smaller. They are less than two feet high. They make a noise rather like a dog barking. In Hong Kong the barking deer has only one r____  enemy- men. People hunt these little animals though it is illegal(犯法的). There are now not many barking deer left. So it is important for people to protect these wild animals.

同类题5

2014年11月16日,******强调,丝绸之路经济带和21世纪海上丝绸之路倡议顺应了时代要求和各国加快发展的愿望,具有深厚历史渊源和人文基础。阅读材料,回答问题。

材料一:“海上丝绸之路”事实上早已存在,中国丝绸的输出,早在公元前便已有东海其航线和南海其航线两条主线路,比陆上丝绸之路的历史更为悠久,是已知的最为古老的海上航线。它形成于秦汉时期,发展于三国时期,唐宋时期,伴随着北方少数民族的活跃以及我国造船、航海技术的长足发展,我国通往东南亚、马六甲海峡、印度洋、红海,乃至非洲大陆航路的分分开通与延伸,“海上丝绸之路”替代了陆上丝绸之路,成为我国对外交往的主要通道。它犹如一条彩带,将古代亚洲、欧洲甚至非洲的文化联结在一起。各国使节、商人往来频繁,中国的四大发明、养蚕丝织技术以及丝绸制品、茶叶、瓷器等,通过海上丝绸之路传送到亚洲、欧洲和非洲的一些国家。同时,中外使节、商人通过丝绸之路,将香料、佛教、音乐、熬糖法、医药,乐器、金银器制作技术、天文学、数学等输入中国。

材料二:在庆祝中法建交50周年之际,我们共同期盼着古老的丝绸之路重新焕发生机与活力。中国和法国,亚洲和欧洲,一起用创新的合作模式,共建“新丝绸之路”。“新丝绸之路”标志着中欧两个文明的再度交汇,汇聚成“思想的丝绸之路”。“思想的丝绸之路”一旦碰撞出新的火花、放射出新的光芒,必将照亮整个世界。