单选题 Our ape-men forefathers had no obvious natural weapons in the struggle for (1) in the open. They had neither the powerful teeth nor the strong claws of the big cats. They could not (2) with the bear, whose strength, speed and claws (3) an impressive " small fire" weaponry. They could not even defend themselves (4) running swiftly like the horses, zebras or small animals. If the ape-men had attempted to compete on those terms in the open, they would have been (5) to failure and extinction. But they were (6) with enormous concealed advantages of a kind not possessed by any of their competitors.
In the search (7) the pickings of the forest, the ape-men had (8) efficient stereoscopic vision and a sense of color that the animals of the grasslands did not (9) . The ability to see clearly at close range permitted the ape-men to study practical problems in a way that lay far (10) the reach of the original inhabitants of the grassland. Good long-distance sight was (11) another matter. Lack of long-distance vision had not been a problem for forest-dwelling apes and monkeys because the (12) the viewpoint, the greater the range of sight-so (13) they had had to do was climb a tree. Out in the open, however, this simple solution was not (14) . Climbing a hill would have helped, but in many places the ground was flat. The ape-men (15) the only possible solution. They reared up as high as possible on their hind limbs and began to walk (16) . This vital change of physical position brought about considerable disadvantages. It was extremely unstable and it meant that the already slow ape-men became (17) still. (18) , they persevered and their bone structure gradually became (19) to the new, unstable position that (20) them the name Homo erectus, upright man.

【正确答案】 A

【答案解析】rival意为“与……相匹敌；比得上”，常用的搭配是rival sb．/sth．for/in sth．；equal意为“比得上，和……相等”，做动词时是及物动词；match意为“和……相配；和……相称”，常用搭配为match with，意为“与……相匹敌”；compare意为“比较；对照”，常用的搭配有compare with，意为“与……相比较”。这里是说“他们无法与熊相比”，故根据句意和搭配，答案应选A。

【正确答案】 D

【答案解析】bestow表示“赠给”，常与on或upon搭配；give一般与to搭配；present表示“赠予”时一般与with搭配；endow表示“天生具有，赋予”，一般用被动式，与with搭配。本句意为“他们却拥有其他任何竞争者所不具有的某种巨大而隐蔽的优势”，故答案选D。

【正确答案】 C

【答案解析】generate意为“生成，产生”；progress意为“进展，进步”，是不及物动词；develop意为“(逐渐)形成”、“(逐渐)获得”，与interest，relationship，ability等搭配；advance意为“促进，提升”。这里是说“在生存竞争中，猿人逐步形成了有效的、草地动物所不具有的立体视觉和颜色辨别的能力”。根据句意，答案选C。

【正确答案】 C

【答案解析】learn意为“学习”，dream of意为“梦想”，possess意为“拥有”，acquire意为“获得”。这里的主语是草原动物，宾语是立体视觉和颜色辨别的能力，那么结合选项就只有possess符合句意。learn和acquire意思类似，但并非表示状态的动词，而是表示点的动作，故不符合句意。

【正确答案】 A

【答案解析】available意为“可得到的，可用的”；enough意为“足够的”；sufficient意为“充足的”；convenient意为“方便的”。上文说的是在森林中居住的猿人和猴子可以通过爬树来扩大视力所及的范围，此处接着说的是，然而在没有树的开阔地带，这种方法是不可行的。故选项A为正确答案。

【正确答案】 D

【答案解析】前面是说他们尽可能地直立使用后肢，那么后面就应当填入直立行走才符合句意，故应当是walk upright。fast肯定是不符合常识的，而stably也不是，因为刚直立行走，必定会有一个适应的过程，不会如此稳定。况且后文也已经说到了unstable。而happily 则无从谈起。

【正确答案】 C

【答案解析】accustomed表示“习惯的，适应的”，常用结构为be accustomed to，意思是“习惯于……”；famifiarized的常用结构为be familiarized with，意思是“与……相熟”；adapt 表示“适应”时，常用adapt to sth．或adapt oneself to sth．结构，暗含作出某种变化以适应新的情况；be suited to sth．表示“适合……的”。这里是说“它们的骨骼渐渐适应了……”，故选项C为正确答案。