问题 单项选择题 共用题干题

在X线摄影中,X线束是以焦点作为顶点的锥形放射线束,将被照体G置于焦点与胶片之间时,因为几何投影关系,一般被照体离开焦点一定的距离a(焦-肢距),胶片离开肢体一定的距离b(肢-片距)。所以,肢体在X线胶片上的影像S要比肢体G大,是被放大了的影像,S与G之比即影像的放大率M,而且胶片离肢体越远,影像放得越大。国际放射学界公认:当照片上的半影模糊值<0.2mm时,人眼观察影像毫无模糊之感;当半影模糊值=0.2mm时,人眼观察影像开始有模糊之感。故0.2mm的半影模糊值就是模糊阈值。

关于几何学模糊,叙述错误的是()

A.焦点尺寸越大,影像越模糊

B.应使被照体靠近胶片

C.0.2mm是半影模糊阈值

D.应减小焦-肢距

E.使用小焦点

答案

参考答案:D

选择题
阅读理解

The Writers’ Strike:Making the Best of the Worst

By now you are probably feeling the effects of the TV writers’ strike-the decision of television writers to stop working. With few new TV shows, I present to you a list of shows available on DVD worth your viewing time to keep you going during this painful period.

Arrested Development is one of the funniest and most clever shows ever to have appeared on network TV. With a most perfect cast, the show sets out to cover the daily happenings of the Bluth family, a group of selfish staff who manage to still put family first.

For more comedy goodness, I recommend one of the sharpest comedies to have ever aired-30 Rock. Starring Tina Fey and Alec Baldwin, two stars with impressive comic timing,the show gives you a glimpse into the making of a sketch show(幽默短剧), similar to Saturday Night Live, from the funny writers to the self­centered cast all the way up to the boss.

If you are looking for something more serious, or perhaps more juicy, Friday Night Lights might be more to your liking. If you are a fan of football, this show is probably for you. If you are a fan of great drama,both soapy and serious,this show is probably for you. If you are a fan of good­looking people, this show is definitely for you.

If those shows were not enough for you, might I recommend a show with a more heart­pounding excitement? The Amazing Race, after twelve seasons, still remains one of the most exciting shows on TV. Teams of two travel the globe with little to no money and experience far­out adventures in an attempt to remain the last team standing.

小题1:If you are fond of soapy TV shows, you will probably choose to watch________.

A.Friday Night Lights

B.30 Rock

C.The Amazing Race

D.Saturday Night Live小题2:From the DVD shows listed above, we can learn that________.

A.two teams won the amazing race

B.football fans enjoy The Amazing Race

C.the Bluths care about their family though selfish

D.30 Rock and Saturday Night Live have nothing in common小题3:The author writes the passage to tell us that________.

A.the effects of the TV writers’ strike are great

B.the strike puts TV shows in the worst situation

C.watching DVD is a good choice during the strike

D.we should choose DVD shows according to our tastes小题4:The passage is most probably taken from        

A.a book review

B.a newspaper

C.a film poster

D.a DVD menu