查找直流接地时，所用仪表内组不应低于（）。

异染性脑白质营养不良可以分为似下哪些类型（）

A.脑型和肾上腺脊髓神经病

B.晚婴型、幼年型、成年型

C.晚婴型、幼年型、青春期型、成年型

D.儿童脑型、青春期脑型、成人脑型

E.肾上腺脊髓神经病型、Addison病型、无症状型

在中小学中提倡

A．努力学习健康知识

B．爱护牙齿从小做起

C．德智体全面发展

D．培养良好卫生习惯

E．定期口腔检查

Waterland, California, June 26,2001—two cars dropped from sight, falling into the bottom (底部) of a 400-feet deep sinkhole (陷洞) which appeared suddenly. At a town 12 miles from Waterland, two bedrooms of one house dropped into a hole 60 feet across and 35 feet deep part of the next house hung dangerously over the hole.

Sinkholes have been happening without warning in this part of California for years. So far there is no way to predict (预告) when or where one will appear. But when one does, others usually follow in the same area, usually along a straight line.

The worst sinkhole in recent appeared in 1996. It was 70 feet across and 150 feet deep. It destroyed in one house, damaged several others and broke the walls of a city block. One hole, 15-feet deep, opened up this year in the middle of a highway, 19 seconds after a car had driven by. Others in the same area took place at night damaging houses, swallowing up trees and parts of streets and making 23 frightened people run away from their homes in night clothes.

Sinkholes happen when the weather is dry. The earth at the surface begins to drop into empty space under the ground, like sand falling in huge hourglass (沙漏). This is how a sinkhole is formed.

71. From the text we know sinkhole do not happen ______.

A. during the period of wet weather              B. in a straight line

C. in the dry season                            D. at night

72. When one sinkhole appears, others usually follow ________.

A. everywhere                                  B. on straight highway only

C. nearby                                     D. in the places far away

73. Sinkholes take place because ________.

A. there are large holes under houses    

B. Waterland has an underground lake

C. there are too many heavy things on the surface of the earth

D. dry earth moves and fills underground holes

74. Which of the following is not talked about in the text?

A. Sinkholes cause car accidents                    B. Sinkholes destroy houses

C. Sinkholes kill people                               D. Sinkholes damage streets

75. This text mainly tells us that ________.

A. sinkholes always happen without any warning

B. sinkholes have been happening in the Waterland area, causing some damage

C. even drivers cannot keep away from sinkholes

D. why a sinkhole happens and how its name has been formed

细胞分裂是生物体一项重要的生命活动，是生物体生长、发育、繁殖和遗传的基础。根据下图回答相关问题：

           图Ⅰ                                图Ⅱ

某种癌细胞培养系中的细胞数目的增加和培养时间的关系如图Ⅲ所示，此癌细胞的细胞周期是（）小时。实验中从图Ⅲ的A点取出6000个细胞，测定每个细胞的核DNA含量，结果如图Ⅳ。若取样的6000个细胞中，处于分裂期的细胞有400个，则处于图Ⅱ所示的CD段时期的细胞有（）个；细胞周期中，完成各期所需时间的计算公式是t＝T×n/N（N是取样的总细胞数，n是各期的细胞数），则该细胞完成图Ⅱ中BC段时期的时间是（）小时。

行政许可需要行政机关内设的多个机构办理的，该行政机关应当确定一个机构统一受理行政许可申请，统一送达行政许可决定。 ( )