资料：It’s easy to trace the evolution of the automobile.At most，we’re only talking about a few centuries of technological development，and most of the plans，prototypes and models are still around. With just a little research，you can easily trace the latest model electric hybrid back to its steam-powered ancestors.
Your family tree is probably a different matter. Even an extensive genealogy chart can only reach back so far，and mortality puts a rather strict limit on exactly how many “models” are still on the road. Humanity’s evolutionary progression is even more difficult. We still have plenty of living primate relatives，but many of the life forms that connect the evolutionary dots are long extinct.
Evolutionary biologists use several methods to decipher exactly how we came to be as we are.In fact，the field itself encompasses several different disciplines in addition to biology，like genetics，psychology，geology，archaeology linguistics，anthropology and primatology just to name a few. Naturally，paleoanthropology also plays a key role，as we have to turn to the fossil record for many clues about our ancient primate，human and nearly human ancestors.
While the fossil record by its very nature is incomplete，there’s no shortage of fossil evidence to link the planet’s varied life forms into a great tree of life， a chart that scientists call a phylogenetic tree. You can think of humans as the very tip of just one branch on that tree called “hominid.” Chimpanzees exist at the end of an adjoining branch called “panin.” Follow both the hominid and panin branch back about 5.4 million years， and you’ll find a point where scientists think the two converged from a single，common ancestor.
Fossil evidence helps scientists to reconstruct these trees，but so do morphological and genetic studlies. Genetic analysis has yielded striking similarities between chimps and humans. As such， scientists know a last common ancestor of chimps and humans existed，even if we’ve yet to determine the exact species. Yet paleoanthropologists have found numerous hominid fossils to bridge the evolutionary progression from that unknown common ancestor to modern humans. These finds include such famous East African fossils as Lucy（Australopithecus afarensis），which strengthened the importance of bipedalism in human evolution and proved an essential milestone on our way to modern Homo sapiens.
Fossil evidence for human evolution will never be complete，as fossils themselves are rare geologic occurrences.Nevertheless，by incorporating other scientific disciplines，we’re able to build an increasingly accurate picture of just what our evolutionary family tree consisted of.
What does the underlined word “bipedalism”refer to in Para.5?
题目意为“第五段中划线词bipedalism意为？”选项A意为“原人和帕宁”，选项B意为“黑猩猩和人类”，选项C意为“用双腿行走”，选项D意为“形态学和遗传学研究”，根据词语在原文位置，只有C项符合文意。
下列关于公司的表述，正确的是（）
以下各项列举了我国常见气象灾害与其发生地区的对应关系，其中正确的一项是（）
根据电视收视率调査，看体育节目的观众中青年人比中老年人要多。
由此可推断出（）
—种海洋蜗牛产生的毒素含有多种蛋白，把其中的一种给老鼠注射后，会使有两星期大或更小的老鼠陷入睡眠状态，而使大一点的老鼠躲藏起来。当老鼠受到突然的严重威胁时，非常小的那些老鼠的反应是呆住，而较大的那些老鼠会逃跑。
以上陈述的事实最有力地支持了以下哪项假说？（）
疾病控制中心对某校髙中三个年级的学生进行抽样做视力状况调查，抽样的方法为分层抽样（按比例抽样），若高中一、二、三年级学生人数分别为626、703、780，样本容量为84，则应从离二年级抽样的学生人数为多少？（）
