20.In general, novels are thought of extended works of prose fiction depicting the inner and outer lives of their characters.

　　答案：A：as extended

　　分析：【think of：to produce an idea, name, suggestion etc by thinking】句中显然不是这个意思，主语是novels是物，若改成主动句，那么这句其实是people think of novels as extended works

　　参考译文：一般说来，小说被看作是散文的延伸，对其(作品里的)人物进行内部心理和外部生活的描述。

　　21.Metabolism is the inclusive term for the chemical reactions by which the cells of an organism transforms energy, maintain their identity, and reproduce.

　　答案：D：transform

　　分析：介词 + which +完整句子;这个从句的主语是the cells of an organism，而判断其单复数要看中心词，这里中心词是cells，所以从句谓语应该是复数。

　　参考译文：新陈代谢是许多生物反应的概括，通过它，组织中的细胞来传递能量，保持独立和繁殖。

　　22.Although most petroleum is produced from underground reservoirs, petroleum occurs in a varieties of forms at the surface

　　. 答案：C：variety

　　分析：由C选项之前的a可以判断，这里应该用可数名词单数variety

　　参考译文：虽然大多数石油是地下沉淀积累产生的，但是地表仍可见多种形式的石油。

　　23.A musical organ can have pipes of two kinds: flue pipes that work like a flute and reed pipes that operate on same principle as a clarinet.

　　答案：D：on the same

　　分析：【the same---as---】的固定用法，少了the;又有on the principle of---按原理

　　参考译文：管风琴有两种类型的音管：flue管(flue没找到合适的解释 )演奏起来像长笛，簧管和单簧管演奏的原理是一样的。

　　24.The Land Ordinance of 1784 divided the western lands belonging to the United States into territories, each to be govern temporarily by its settlers.

　　答案：C：governed

　　分析：仅通过简单的结构判断，从画线部分前后就可知这里govern应该改成动词被动形式;be是系动词，govern是动词，不用被动则造成冲突;temporarily是个副词，后置于动词之后修饰该动词，所以还是判断改成动词的被动形式;【(be)done + by +doing】这个结构在托福中可谓是真理。

　　参考译文：1784年(颁布)的土地法把属于美国的西部地区分成了(一个一个的)州，每一个都被当地的居民临时管辖着。

　　25.If there is too much pituitary hormone of too few insulin, the amount of sugar in the blood rises abnormally, producing a condition called. Hyperglycemia.

　　答案：B：little

　　分析：单从insulin的数量上就可以做出选择，不难，前面也有too much的暗示。(根据生物学原理，胰岛素分泌少才导致高血糖)

　　参考译文：(意译)若是有很多脑垂体下分泌出荷尔蒙而有很少的胰岛素，血糖就会上升很快，这种现象叫做高血糖。

　　26.The care of children during their years of relative helplessness appears to have being the chief incentive for the evolution of family structures.

　　答案：C：been

　　分析：have在这里做助动词，而不是“有”的意思，用过去分词been

　　参考译文：在孩子相对无助的年龄阶段所对他们的关怀似乎成了家庭结构演变的主要动因。

　　27.It was not until the 1920’s that pollution came to be viewed by many as a threat to the health of live on Earth.

　　答案：D：lives

　　分析：live可以做动词，副词，形容词，就是不能做名词;这里应该是life的复数。

　　参考译文：直到二十世纪二十年代，污染才被大多数(人)视为威胁地球上生命健康。

　　28.Platelets are tiny blood cells that help transport hormones and other chemicals throughout the body, and it play a role in clotting blood.

　　答案：C：they

　　分析：it无从正确指代，本应改指代platelets的;或者简单的从play这个未画线的动词的数上就可以判断。

　　参考译文：血小板是很微小的血细胞，他能帮助荷尔蒙和许多化学物质运输到整个身体，并且在凝血中也起了很重要的作用。

　　29. Until the twentieth century, pendulum clocks were calibrated against the rotation of earth by taking astronomically measurements.

　　答案：D：astronomical

　　分析：measurements是名词，修饰名词应该用形容词，astronomical天文学的adj.

　　参考译文：直到二十世纪，(意译)摆钟才通过天文方面的方法被校准，从而摆脱了地球自转的影响。