题干

下列有关哺乳动物胚胎发育和胚胎工程的叙述正确的是

A:超数排卵技术要使用一定的激素如性激素、孕激素等

B:滋养层细胞发育成胎膜和胎盘是在囊胚期

C:卵裂期胚胎中细胞数目和有机物总量在不断增加

D:胚胎移植实际上是由提供胚胎的供体和孕育胚胎的受体共同完成的

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答案(点此获取答案解析)

D

同类题2

阅读下文,完成小题。

家徽

余华

       ①国有国徽,校有校徽,厂有厂徽。奇怪吗?我家竟有家徽。我们家的家徽是一条鱼,一条画在门板上的鱼。那条鱼的图案画得很笨拙,线条零乱而粗糙,只能让人意会到是条鱼而已。但它却有不寻常的来历。

       ②祖父在世时,膝下有父亲他们弟兄四个,个个都是牛高马大的男子汉。战乱时期,家庭仗着几个男人下死力气勉强维持温饱。

       ③一天夜半,父亲起来小解,发现一个人影窜进了厨房,他便喊叫起来,同时马上守住厨房门口。不一会儿,父亲弟兄几个都起来了,他们点着灯,拿着大木棒子和斧头,仔细地搜索着厨房的每一个角落,那时粮食就是性命,大家决心不把这窃贼打死,也得让他残废。厨房的旮旮旯旯都搜遍了,却没发现人。父亲弟兄几个说父亲定是半夜眼花,父亲赌咒发誓说肯定有人。还在大家争辩时祖父来了,祖父让儿子们都去睡觉。等他们走了后,祖父走到水缸边,敲敲盖子,说:“你不用躲了,出来吧。”只见水缸里水淋淋地站起一个人。这人一手擎着水缸木盖,浑身颤抖,面无人色,另一只手里,还攥着一布袋大米。

       ④祖父望着窃贼,叹口气说:“算了,你走吧,要是让我的儿子们看见了,你今天非残废不可。”

       ⑤贼傻望着祖父,他不敢相信祖父就这样轻易地让他走,但祖父分明是平静地挥了挥手,贼便从水缸里爬出来。祖父又把那水淋淋的米袋子交给他说:“带上它吧,它可帮你家度几天日子。”贼要说什么,眼眶却红了,低着头,提着米袋子往外走,走到门口,“慢着,”祖父又叫住他,塞给他一串铜钱,“你拿这钱去做点小生意,再也不要干这伤天害理的勾当了。”

       ⑥贼“扑通”一声跪在地上,给祖父磕了几个响头便走了。

       ⑦不知过了多久,一天清晨,祖父一开门,便在门环上发现了一条两斤多的鲜鱼。祖父先是感到奇怪,但他马上就猜到是那贼送来的,那人大约是做了贩鱼的生意。

       ⑧自此以后,我家门环上经常出现鲜鱼,家里便经常可以改善生活。父亲他们感到奇怪,祖父便舒缓地向父亲弟兄们讲起鱼的来历。

       ⑨大约吃了几十条鱼后,祖父感到不安,说人家是小本经营,别吃垮了人家。于是连着几天半夜守候着,一直熬了三个夜,终于让祖父遇见了那送鱼人,谁知不是那个贼,却是一个年轻渔人。这渔人是那贼的儿子,贼在临终前嘱咐他要坚持送鱼到我家来。祖父和父亲他们听得连连点头。为了不违亡人遗愿,祖父拿过一把刀子,让年轻人在我家门上刻一条鱼,并说从此不许他再送鱼,就用这条刻下的鱼替代好了。祖父并叮嘱父亲弟兄们要保管好这条“鱼”,牢记这件事。于是,我家按照祖父的意思,每次做屋或换门时,一直都保留着这鱼的图案。

       ⑩它,自然而然地成了我家的家徽。

(文章有删改)

同类题3

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      A glass a day keeps obesity at bay. Wine has always been thought to cause weight gain because of its high sugar content, but new research suggests a glass a day could form part of a diet. Looking at past studies they found that, while heavy drinkers do put on weight, those who drink in moderation can actually lose weight.

    A scientist for the research team at Navarro University in Spain says, “Proper drinking may be more likely to protect against, rather than promote, weight gain.” An official organization reviewed the findings and agreed with most of the conclusions, particularly that present data do not clearly show if proper drinking increases weight.

    Boston University's Dr. Harvey Finkel found that the reasons relating alcohol (酒精) to changes in body weight are not properly understood. His team pointed out the strong protective effects (效果) of proper drinking on the risk of getting conditions like diabetes (糖尿病), which relate to increasing obesity. Some studies suggest that even very fat people may be at lower risk of diabetes if they are moderate drinkers.

    The group says alcohol provides energy that is quickly absorbed into the body and is not stored in fat, and that this process could explain the differences in its effects from those of other foods. They agree that future research should be directed towards assessing the roles of different types of alcoholic drinks, taking drinking patterns into consideration.

    For now there is little evidence that drinking small to moderate amounts of alcohol on a regular basis increases one's risk of becoming too fat. What's more, a study three years ago suggested that a chemical found in grapes and red wine, destroys fat cells.