[简答题]Why is it that there are not more scientists in the field according to the speaker

[单项选择]Scientists have known for more than two decades that cancer is a disease of the genes. Something scrambles the DNA inside a nucleus, and suddenly, instead of dividing in a measured fashion, a cell begins to copy itself furiously. Unlike an ordinary cell, it never, stops. But describing the process isn’t the same as figuring it out. Cancer cells are so radically different from normal ones that it’s almost impossible to untangle the sequence of events that made them that way. So for years researchers have been attacking the problem by taking normal cells and trying to determine what changes will turn them cancerous - always Without success.
According to a report in the current issue of Nature, a team of scientists based at M. I .T.’s Whitehead Institute for Biomedical Research has finally managed to make human ceils malignant -a feat they accomplished with two different cell types by inserting just three altered genes into their DNA. While these manipulations were done only in lab d
A. how cancer ceils are formed
B. why cancer cells never stop dividing
C. why normal cells can turn into cancer cells
D. how different normal cells are from cancer cells

[单项选择]How and why this language has survived for more than a thousand years，while spoke by very few，is hard to explain. 　　A B C D

[填空题]The reason why we should be eating more fish is that ______.

[填空题]Scientists now understand why people’s mental faculties decline at different rates.’

[判断题]
Scientists do not understand why women should outlive men by five years.

[单项选择]How many times is the indoor air more hazardous than the outdoor air
A. 10 to 12.
B. 12.
C. 2 to 10.
D. 2.

[单项选择]Few articles in the newspapers （）more attention than that reporting the murder case with O.J. Simpson involved
A. enlist     
B. divert     
C. draw     
D. absorb

[填空题]The intake of side-stream smoke is more harmful than smoke exhaled by a smoker.

[单项选择]What is scientists’ attitude towards the saying that dreams about future will come true
A. Positive.
B. Negative.
C. Neutral.
D. Not mentioned.

[单项选择]Why are scientists interested in Mars（）
A. Because people might have to migrate there someday.
B. Because it is very much like the earth.
C. Because it is easier to explore than other planets.
D. Because its atmosphere is different from that of the earth.

[简答题] Scientists have learned more about the way cancer spreads from one place in the body to another. Once it spreads, it gets more difficult to treat. Cancer is a disease of uncontrolled cell growth. Traditional thinking is that cells simply break off the main cancer, travel through the blood and grow in other organs. But the new findings suggest there is more to this process. Researchers found that cells from the main tumor send out messengers. These prepare the new organ for a secondary tumor (瘤). It works this way. The primary tumor releases proteins called growth factors into the blood. They signal cells at the target organ to produce a sticky protein, called fibronectin. It attaches to the surface of bone marrow (骨髓) cells. The result is a kind of landing area for cancer to arrive and grow into a secondary tumor. The bone marrow cells help make vessels for blood to pass through and feed the cancer cells. The researchers believe that without the bone marrow cells, the tum