高能射线是能量在1Mev以上的X射线,采用直线加速器产生的高能X射线与一般X射线相比,具有()等特点。
A. 穿透能力强
B. 焦点小
C. 转换效率高
D. B和C
根据下列材料,回答下面的题目 For the 26 month.mysterious falls of large chunks of ice(冰雹) 27 rained down on Spain and Italy.Juana Sanchez。a 70一year—old woman in Almeria,southern Spain,was knocked 28 when she was struck on the shoulder by a falling ice chunk 29 she walked in a street 30 her home.On January l2,just about 200 miles away in Seville,a man narrowly 3l serious injury when a 9-pound ball of ice32into his car.33 me evening of January 27 priests at the salesian monastery in L,Aquila,Italy were startled by.a loud crash. 34 the noise,the dlscovered a large chunk of ice on their yard,35 intact. Upon examination。the block of ice 36 in at 2 kilograms and no source 37.On the same day,about l00 miles northeast in Ancona,Italy,the local officials were called to investigate the report of a maIl 38 was struck 39 the head by a l kilogram chunk of ice that apparently fell from the sky. spain and Italy area"the only European40 getting attacked by huge ice blocks in January On JaIluary 2 in Surrey,England(southwest of London),an East Indian man was walkingthrough Newton Amletic Park when he41a strange whistling sound overhead.‘Seconds 42 ,a large hunk of ice fell out of the clear blue sky and pounded in‘to the soft ground,shattering over a 50 foot—wide area.The ice dug a hole of a foot deep and a foot in di锄eter. Even the shattered remnins of the mystery ice were as large as tennis balls and were described as opaque 43 no unusual color or smell. Although eyewitnesses to the phenomenon report that they did not see anything in the sky that could account 44 the ice,scientists had to come up with a rationalization.Professor Jesus Mar tinez Frias,the geologist investigating the ice falls in Spain,told BBC News t}lat me ice Dieces had probably been 45through sudden temperature drops in the stratosphere.nlis was the most like1y explanation,he said,for the‘‘very unusual”phenomenon.
A. large
B. largely
C. big
D. huge
()是一个人为了获得自己所附属的长者(家长、教师)的赞许和认可而表现出来的把工作做好的一种需要。学生努力求得学业成就,是为了从长者那里得到赞许和认可。
A. 认知内驱力
B. 附属内驱力
C. 自我提高内驱力