问题 单项选择题

先天性梅毒牙

A.成釉细胞增生突人牙 * *
B.牙齿发育时牙 * * 组织向成釉器突起
C.釉牙本质界平直
D.釉基质合成、分泌或矿化障碍
E.局限性釉质增生

答案

参考答案:A

解析: 畸形中央尖的发生是由于牙发育时期牙 * * 组织向成釉器突起,在此基础上形成釉质和牙本质。釉珠是局限性釉质增生的结果。釉质发育不全又称釉质形成缺陷症,主要形成原因是釉质发育期釉基质合成、分泌或矿化障碍。遗传性乳光牙本质属牙本质形成缺陷,髓腔表面仅见少量不典型的成牙本质细胞,釉牙本质界呈直线而非波浪型。先天性梅毒牙是牙冠形成期梅毒螺旋体侵入牙囊,引起牙囊慢性炎症及纤维化,挤压正在发育的牙胚,引起成釉细胞增生而突人牙 * * 。

单项选择题
单项选择题

Low levels of literacy and numeracy have a damaging impact on almost every aspect of adults, according to a survey published yesterday, which offers (1) of a developing underclass. Tests and (2) with hundreds of people born in a week in 1958 graphically illustrated the (3) of educational underachievement. The effects can be seen in unemployment, family (4) , low incomes, depression and social inactivity.

Those who left school at 16 with poor basic skills had been employed for up to four years less than good readers (5) they reached 37. Professor John Bynner, of City University, who carried the research, said that today’s (6) teenagers would even encounter greater problems because the supply of (7) jobs had shrunk.

Almost one fifth of the 1,700 people interviewed for yesterday’s report had poor literacy and almost half (8) with innumeracy, a proportion (9) other surveys for the Basic Skills Agency. Some could not read a child’s book, and most found difficult (10) written instruction.

Poor readers were twice as likely to be a low wage and four times likely to live in a household where partners worked. Women in this (11) were five times as likely to be (12) depressed, (13) both tended to feel they had no control over their lives, and to trust others (14) .

Those who had low literacy and numeracy were seldom (15) in any community organization and less likely than others to (16) in a general election. There had been no (17) in the literary level of (18) reporting problems.

Alan Wells, the agency’s director, said: “ The results emphasize the dangers of developing an underclass people, who were out of work, (19) depressed and often labeled themselves as (20) . There is a circle of marginalization, with the dice against these people and their families.”

2()

A.investigations

B.interviews

C.conferences

D.communications