4.关于辐射的分类，以下说法错误的是

A、电磁波主要向水平方向呈扇形发射，随距离增加而衰减B、由于墙壁等障碍物的遮挡，导致正下方的辐射衰减很快C、基站正下方的辐射大D、即使每天与基站设备为邻，所受到的电磁影响，比家里新添一件电器的影响还要微弱的多

以下关于射电星系的说法错误的是A、射电辐射功率很高，在频率为10MHz~100GHz之间的辐射功率最高可达WB、射电星系基本都是漩涡星系C、射电星系都具有喷流结构D、射电辐射主要来自同步辐射机制

A.燃油经雾化后与空气一起进入燃烧室，由于油滴的表面摩擦阻力会使油滴速度迅速衰减而达到与空气流速相等，所以油滴的蒸发燃烧过程可以近似看作是在运动空气中进行的B.油滴进人燃烧室后，受到火焰辐射和燃烧产物的扩散传递的加热，油滴表面的燃油蒸发形成油气向周围气体扩散并在油滴附近被点燃，形成球形火焰面C.油雾是由许多粒度不等的油滴所组成D.油滴在相互十分靠近的条件下燃烧时，一方面它们的扩散燃烧火焰锋面相互传热，另一方面又相互妨碍着氧扩散到它们的火焰锋面

以下哪个陈述不是齐白石的艺术特色（ ）

A、用笔苍辣古拙

B、充满童趣天真

C、吸收民间绘画色彩和图式，简率热烈

D、画风飘逸高远，充满文人画的隐逸气质

A、44.2MPa

B、46.9MPa

C、42.8MPa

D、48.5MPa

A、特殊的

B、含有数字的

C、重要的，主要的

D、出现最多的

在图所示机构位置时，杆铅直，其角速度为，AD杆水平，DE杆与水平线成45°角，杆与杆DE垂直。已知，滑块E在铅直槽内滑动，则此时滑块E的速度大小为为（ ）

A、

B、

C、

D、

A、桂枝

B、羌活

C、白芷

D、荆芥

Millriver is a tiny village. Someone says it possesses a tree. The tree is cursed. Someone mentioned the tree in a newspaper. People visit Millriver. The number has now increased. The tree near a church. Someone planted it fifty years ago. It is only in recent years. It has gained an evil reputation. People say that anyone touches the tree will have bad luck, picks a leaf will die. The tree has already claimed a number of victims. Many villagers believe. They has been asked the vicar to ask others cut down the tree. Up to now he has refused. He has pointed out. The tree is a useful source. People can get income from it. Tourists have been coming to see it. They are from all parts of the country. People all said that. The tourists have been picking leaves and cutting their names on the tree-trunk. Up to now, there are no men has been struck down by sudden death!

A、普通口罩即可达到要求

B、普通口罩的作用是防尘，能够把灰尘挡住，也能挡住PM2.5

C、戴口罩的时候是完全密封的，能够完全阻挡PM2.5

D、阻挡PM2.5进入人体，要戴专业的口罩，比如N95口罩