问题 单项选择题 A1型题

下颌第二乳磨牙和下颌第一恒磨牙形态近似位置彼此相邻,容易混淆,下列哪项不是第二乳磨牙的特点()

A.牙冠短小,色白

B.牙冠颈部明显缩小,颈嵴特突,牙冠由颈部向方缩小

C.近中颊尖、远中颊尖及远中尖的大小约相等

D.第二乳磨牙的根干短,牙根向外张开

E.近中颊尖、远中颊尖大小相等,远中尖最小

答案

参考答案:E

解析:下颌第二乳磨牙牙冠较第一恒磨牙小、色乳白;牙冠近颈缘明显缩小,颈嵴突出,牙冠向方缩小,故近颈部大而面小;近中颊尖、远中颊尖及远中尖大小约相等(E错),而下颌第一恒磨牙此三尖中,远中尖最小;上颌第二乳磨牙为三根,下颌者为双根,根柱短,牙根向周围张开,所以选E。

阅读理解

阅读短文,根据短文内容回答问题。

Every year, wildfires(野火) destroy much forest land. homes are broken down, and thousands of people die. smokejumpers are stop helping to stop this.

Smokejumpers are a special kind of firefight. they jump from planes into areas that difficult to reach by car or on foot. they race to put out fires as fast as they can.

At a fire site, Smokejumpers first examine the land and decide how to fight the fire. their main goal is to stop fire from spreading. using basic tools such as shovels and axes, smokejumpers clear land of burnable material like plants and other dry material. they carry water with them too, but not much.

Although most smokejumpers are men, more women are joining. Most important are your weight and height. Smokejumpers in the U.S. for example ,must be 54 to 91 kilograms, so they don’t get hurt when they land, or get blown by strong winds.

Smokejumpers must be able to live in the wilderness. in Russia ,many smokejumpers know how to find food in the forest and even make simple furniture from trees.

They work is dangerous, the hours are long. But for these firefighters, smokejumpers isn’t just a job. They love being able to jump out of planes, fight fires, and live in the forest. As 28-year-old Russian smokejumpers Alexi Tishin says,“This is the best job for the strong and brave.”

小题1:What are Smokejumpers?

小题2:Where do the jump from?

小题3:What’s their main goal?

小题4:Why should they have proper weight?

小题5:What’s needed to be a smokejumpers?

填空题