含有稀土元素的萤石,经日光照射后可持续发光数十小时,民间称之为“夜明珠”。萤石的

题型:选择题

问题:

含有稀土元素的萤石,经日光照射后可持续发光数十小时,民间称之为“夜明珠”。萤石的主要成分氟化钙(CaF2)中氟元素的化合价为[ ]

A.+1

B.+2

C.-1

D.-2

考点:化合价的求法
题型:选择题

倍压电路主要是利用一个电容器所充得的电压和电源电压叠加后,再给另一个电容器充电,而使后一个电容器得到的电压是电源电压的二倍,依次类推,可以获得二倍、三倍…等许多倍电压。

题型:选择题

下列那哪部作品是青主先生的音乐专著:()

A、《乐话》

B、《大江东去》

C、《我住长江头》

D、《清歌集》

题型:选择题

以下不是中日文人交往方式的是()

A、笔谈

B、唱和汉诗

C、携带翻译

D、朝贡贸易

题型:选择题

全国人民代表大会常务委员会对宪法和法律所作的解释属于( )。

A.审判解释
B.立法解释
C.司法解释
D.行政解释

题型:选择题


Directions: There are 10 blanks in the following passage. For each numbered blank, there are four choices marked A, B, C and D. Choose the best one and mark your answer on the ANSWER SHEET with a single line through the center.

Our planet is like a bit spaceship. Our atmosphere acts (51) a shield against harmful radiation and space debris. (52) holds the air and people on the spaceship, (53) everything doesn’t float away. Each of us is an astronaut and our spaceship, the earth, provides our food and water. The sun is our energy (54) and without it we would not be able to survive.
(55) every spaceship, the earth is a closed system. The only thing we receive from the outside is energy from the sun. Everything else must be used (56) again. We astronauts don’t seem to realize that this spaceship is the (57) one we’ve got. We (58) its resources and waste the energy the plants have stored from the sun. If we (59) our spaceship, we will destroy ourselves as well. Maybe if we look at the universe which surrounds us, we will appreciate our own spaceship more and take (60) care of it.

A.Granite

B.Gravity

C.Gratitude

D.Grace

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