对称三相交流电每相相位差为（）。A.0° B.60° C.120° D.90°

As if there weren’t enough of them in the world already, scientists have succeeded in cloning flies. The alike fruit flies are the first insects ever cloned, says the Canadian team that created them. The question everyone asks is why anyone would want to clone flies in the first place. She hopes that the insects , which are very easy to experiment with , will help to adjust the cloning process in other animals and even in humans, where the technique is being researched to aid production of therapeutic (治疗的) stem cells.

In cloning, the DNA-containing nucleus of an adult cell is injected into an egg whose own nucleus(细胞核) has been removed. At the moment, the majority of cloned mice, sheep and other animals die before birth. It is thought this is because the adult DNA is not properly ‘reprogrammed’.

Using flies, researchers might discover genes that are important for this reprogramming, and that have matches in other animals. That is because it is relatively easy in flies to knock out the function of a single gene and then attempt cloning with these cells, which will test whether that gene is important. If such genes are confirmed, then in theory cloned mammalian embryos(晶胚) might be grown in selected solutions that change the activity of those genes to improve the technique’s success rate. Although some groups have attempted to clone insects before, Lloyd says this is the first time it has been successful. The team used a slight difference on the standard cloning process: they transferred nuclei taken from embryos rather than fully-grown adult cells. They sucked several nuclei (pl)out of developing fly embryos, and injected them into a fertilized(已受精的) fly egg. From over 800 early attempts, they cloned five adult insects, the group reports in the journal Genetics.

小题1:The best title of this passage probably is _______.

A．The importance of clone

B．First insects are cloned

C．The disagreement in clone

D．The advantages of clone小题2:The scientists cloned flies because________.

A．there are fewer and fewer flies in the world

B．flies are easy to find and cheap to use

C．they can gain some experience before cloning other animals

D．it is safe to clone flies小题3:The failure of most cloned animals is due to _______.

A．the difference of other animals’ genes

B．the improper technique of clone

C．the complex of other animals

D．the improper rearrange of the adult gene小题4:It can be inferred from the last paragraph that ______.

A．the clone of insects before used grown-up cells

B．the clone of insects were never experimented before

C．this time scientists cloned flies successfully and easily

D．based on this success, other animals will be cloned in large quantities.

与人心肌组织具有共同抗原（）

A．大肠杆菌O14

B．溶血性链球菌

C．变形杆菌OX19

D．大肠杆菌O86

E．肺炎球菌14型

电位滴定法测定混凝土外加剂氯离子含量，测定时使用的标准溶液为（）。

A.硝酸

B.硝酸银溶液

C.氯化钠溶液

D.盐酸溶液

肌力训练的原则有哪些？

我国高等药学教育开设药事管理学课程始于20世纪40年代。（）