下列计算中，正确的是（   ）

请从H、C、N、O、Na、Cl、K、Ca中选取相关元素，用合适的化学用语填空。

据调查：目前大部分中学生与父母在穿衣打扮、业余爱好、课外读物、交友等问题上存在着不同程度的分歧，感觉与父母总是谈不到一块去，出现话不投机半句多的情况。

如图，在矩形ABCD中，点A为坐标原点，点B在x轴正半轴，点D在y轴正半轴，点C坐标为（6，m），点E是CD的中点，以CE为一边在矩形ABCD的内部作矩形CEFG，使点F在直线y=x上，交线段BC于点G，直线DG的函数表达式为y=- $\frac{1}{6}$ x+4，直线DG和AF交于点H．

阅读理解

    Many people today like reading stories about UFO.Many people in different countries are studying the UFO.

    There are some different saying for UFO.Among those sayings,the most popular one for UFO is that UFOs are strange creatures(生物) to the earth from other stars.We can call them aliens.

    UFO scientists and many people believed this saying.Some people said that they saw a few UFOs landing on the earth.They seemed to be objects rather like big plates.Some people said that they saw some strange visitors coming out of the UFOs.

    Some people make mistakes when they say they have seen UFOs high in the sky.Perhaps they see a weather balloon or an uncommon plane or the light they see in the sky comes from the ground.Sometimes they see the light from the moon.

    But these are a lot of others we can't understand.It may take many years to find a clear answer and then people will give UFO another name.