課后練習：

1. This is called background radiation and levels vary from place to place, though the average dose is fairly________.

A. constantB. contactC. contentD. construct

2. While artificial radiation________a small proportion of the total, its effects can be disproportionate.

A. accounts toB. accounts ofC. accounts inD. accounts for

3. It has never been shown that there is ________a thing ________a safe dose of radiation.

A. such; asB. A. such; so C. A. so; asD. A. such; to

4. In general, the effects of radiation can ________those which affect the individuals exposed and those which affect their descendants.

A. be divided inB. be divide intoC. divided into

D. be divided into

5. Some of these are released into the environment, for example iodine and carbon, two common elements ________.

A. used by our bodiesB. be used by our bodies

C. are used by our bodiesD. A. used our bodies

6. Strontium deposits in the bones send radioactivity into the bone marrow, ________the blood cells are formed, causing leukemia.

A. whichB. whereC. thatD. while

7. There are three ________ effects which radiation can have on cells.

A. principalB. principally C. principle

8. In most cases, cell death only becomes ________ when large numbers of cells are killed.

A. significantly B. significant C. abundantD. abundantly

9. Ionizing radiation can damage DNA, the molecule which acts________the cell's "instruction book".

A. inB. outC. asD. toward

10. It may ________increase sufficiently in size to form a detectable cancer.

A. ultimateB. ultimatelyC. ultimacy

11. The fact that the populations ________(bomb survivors, people exposed to nuclear industry) are small.

A. being studiedB. studiedC. be studied

通過本課學習，要重點掌握“非謂語動詞”相關語法的內容。簡述如下。

• 非謂語動詞包括分詞和動名詞。

• 分詞的種類：現在分詞(the Present Participle)和過去分詞(the Past Participle)

• 分詞的作用：主要起形容詞和副詞作用，在句子中做狀語、定語、補語或表語。

• 分詞的區別：現在分詞具有主動意義或表動作正在進行；過去分詞中及物動詞的過去分詞具有被動意義，或表動作已完成；而不及物動詞的過去分詞具有主動意義，如a fallen leaf。

• 分詞的時態和語態：

• 動名詞是具有動作含義的名詞，在句子中做主語、賓語或表語；其時態和語態與現在分詞相同。

溫馨提示：個人認為本課（Radiation and Human Health輻射與人體健康）內容與我們的生活息息相關，而且是科學類的文章，“閱讀理解”與“翻譯”出題的可能性較大，應認真閱讀。

result in結果是…，后面跟的是導致的結果
result from起因于；由…造成，后面跟的是導致的原因
例如：They result in poor capital allocation.它們會導致資本配置不當。
Losses in honey bee populations can result from a number of causes. 蜜蜂群體的損失是由很多原因造成的。