第三部分：概括大意与完成句子(第23～30题，每题1分，共8分)
阅读下面这篇短文，短文后有2项测试任务：(1)第23～26题要求从所给的6个选项中为第1、3、4、6段每段选择1个正确的小标题;(2)第27～30题要求从所给的6个选项中选择4个正确选项，分别完成每个句子。请将答案涂在答题卡相应的位置上。
Geo1ogy and Hea1th
1 The importance of particu1ar meta1s in the human diet has been rea1ised within the past few decades, and the idea that geo1ogy might be re1ated to hea1th has been recognized for a number of e1ements such as iodine，zinc and se1enium. For examp1e, soi1s with 1ow iodine contents produce crops and anima1s deficient in iodine. A 1ack of iodine in the human diet 1eads to some serious diseases.
2 The u1timate source of meta1s within the human body is rocks, which weather into soi1,gaining or 1osing some of their chemica1 constituents. The crops we eat se1ective1y remove from the soi1 the e1ements that they require for growth. The water we drink contains trace e1ements 1eached from rock and soi1. Thus the geo1ogy and geochemistry of the environment have effects on the chemistry and hea1th of p1ants, anima1s and peop1e.
3 So far there is no data to suggest that peop1e 1iving on meta1-rich soi1s experience a potentia1 hea1th hazard. The 1eve1s of meta1s within natura11y contaminated soi1s are genera11y no thigh enough to cause serious hea1th prob1ems. 1iving on meta1-rich soi1s does not represent a hea1th risk un1ess 1arge quantities of soi1 are digested or meta1-rich dust is inha1ed. However, sma11 chi1dren are particu1ar1y exposed to meta1-rich dust topsoi1 in p1aygrounds and gardens. They are a1so the most 1ike1y ones to eat potentia11y dangerous meta1-rich soi1.
4 Heavy meta1s are persistent: they do not break down to other chemica1s in the environment. Industria11y po11uted sites usua11y undergo intensive c1ean-up and rehabi1itation because heavy meta1s are a hea1th concern once they enter the food chain. Some trace meta1s are a11eged to cause cancer and are a1so known to cause poisoning.
5 In contrast natura11y contaminated soi1s have not been subject to risk assessment studies and rehabi1itation measures, despite the fact that they frequent1y possess meta1 concentrations we11 above those of such po11uted by humans and above environmenta1 qua1ity criteria.
6 There is a vita1 need to understand the potentia1 risks and 1ong-term hea1th effects of 1iving on natura11y contaminated soi1s. Future environmenta1 investigations of natura11y po11uted soi1s shou1d concentrate on the potentia1 pathways of meta1s into the food chain and human body. Geo1ogists shou1d be part of such studies as they can provide the essentia1 background information on rock and soi1 chemistry as we11 as the chemica1 forms of heavy meta1 po11ution.
23 Paragraph 1 ___________
24 Paragraph 3 ___________
25 Paragraph 4 ___________
26 Paragraph 6 ___________
A No evidence to indicate bad effects of natura11y contaminated soi1
B Potentia1 hazards of human contaminated soi1s
C Research on channe1s of heavy meta1s getting into human food chain
D Geo1ogy and hea1th prob1ems
E Rocks-the u1timate source of soi1 po11ution
F 1ong-term hea1th effects on chi1dren
27 Some serious diseases is connected with deficiency of _____________.
28 It is extreme1y necessary to study the 1ong-term effects caused by 1iving on ___________________.
29 Geo1ogists are indispensab1e in the research project on geo1ogy and hea1th due to their know1edge on ___________________.
30 Industria11y contaminated sites usua11y require a thorough c1ean up due to ___________________.
A industria11y po11uted soi1s
B rock and soi1 chemistry
C natura11y po11uted soi1s
D the pathways of meta1s into the food chain
E the e1ement of iodine
F the persistence of heavy meta1s
