1. _________ directly with most metals to form compounds called carbides.
A. Carbon reacting
B. Carbon reacts
C. The reaction of carbon
D. When carbon reacts
答案：B
分析：從句意來看，called在這里不是謂語動詞，而是分詞做后置定語：…… which are called carbides.空格中缺主語和謂語，選B.
參考譯文：碳直接跟大部分金屬反應而形成碳化物的化合物。
2. Meteorites are slowed down by Earth's atmosphere， but if they are moving _________， they can form a crater on impact.
A. enough fast
B. fast enough
C. so fast enough
D enough are fast
答案：B
分析：enough的用法，固定順序：adj.+enough
參考譯文：隕石受地球大氣阻擋而慢下來，但如果他們移動的足夠快，他們能在撞擊后形成一個大坑。
3. Located at the upper end of each________ an adrenal gland， an integral part of the endocrine system.
A. kidney which is
B. kidney is
C. kidney being
D. kidney
答案：B
分析：該句為簡單句，而且使用了倒裝形式，原句為：An adrenal gland， an integral part of the endocrine system is located at the upper end of each kidney.
參考譯文：腎上腺是內分泌系統的一個完整的部分，它位于腎的上端。
4. About 75 percent of all cadmium is used for cadmium plating of _________ such as iron and steel.
A. easily corroded metals
B. metals are easily corroded
C. corroded metals that easily
D. how easily metals corroded
答案：A
分析：B中的are多余，否則句中出現兩個謂語，錯;C中的that引導定語從句，而從句缺謂語，錯;用法錯誤，of后一般接名詞。
參考譯文：75%的所有鎘金屬都用來對類似鐵、鋼的容易腐蝕的金屬進行鎘鍍膜了。
5. An atom is a basic structural unit of matter， the smallest particle of an element _________ into chemical combination.
A. that can enter
B. can it enter
C. when entering it can
D. that enters can
答案：A
分析：that引導定語從句，element為先行詞。the smallest particle of an element 是 a basic structural unit of matter的賓語同位語。
參考譯文：原子是物體的基本結構單元，是元素形成化學組合特性的最小的顆粒。