According to Weis in the 5th paragraph, the theory of evolution ______.

Bill can inspect a case of cell phones in 6 hours. Jack can inspect the same case of cell Phones in 4 hours. After working alone for l hour, Bill stops for lunch. After taking a 30-minute lunch break. Bill and Jack work together to inspect the remaining cell phones. How long do Bill and Jack work together to complete the job?

The consistent burning of fuel oil with a high sulfur content in a diesel engine will result in （）

The burning of fuel oil in a diesel engine having a high sodium content, will cause （）

Which of the following best explores American dream in the 20th century? _____

[A] The work builds on a study published last year by Shinya Yamanaka of Kyoto University in Japan, which showed that mouse tail cells could be transformed into ES-like cells by inserting four genes (Science Now, 3 July 2006).Those genes are normally switched off after embryonic cells differentiate into the various cell types. In June this year, Yamanaka and another group reported that the cells were truly pluripotent, meaning that they had the potential to grow into any tissue in the body (Science Now, 6 June).
　　[B] In the new work, Yamanaka and his colleagues used a retrovirus to ferry into adult cells the same four genes they had previously used to reprogram mouse cells: OCT3/4, SOX2, KLF4, and c-MYC. They reprogrammed cells taken from the facial skin of a 36-year-old woman and from connective tissue from a 69-year-old man. Roughly one iPS cell line was produced for every 5,000 cells the researchers treated using the technique, an efficiency that enabled them to produce several cell lines from each experiment.
　　[C] Now the race to repeat the feat in human cells has ended in a tie: Two groups report today that they have reprogrammed human skin cells into so-called induced pluripotent cells (iPSs). In a paper published online in Cell, Yamanaka and his colleagues show that their mouse technique works with human cells as well. And in a paper published online in Science, James Thomson of the University of Wisconsin, Madison, and his colleagues report success in reprogramming human cells, again by inserting just four genes, two of which are different from those Yamanaka uses.
　　[D] Once the kinks are worked out, “the whole field is going to completely change,” says stem cell researcher Jose Cibelli of Michigan State University in East Lansing. “People working on ethics will have to find something new to worry about.”
　　[E] Thomson’s team started from scratch, identifying its own list of 14 candidate reprogramming genes. Like Yamanaka’s group, the team used a systematic process of elimination to identify four factors: OCT3 and SOX2, as Yamanaka used, and two different genes, NANOG and LIN28. The group reprogrammed cells from fetal skin and from the foreskin of a newborn boy. The researchers were able to transform about one in 10,000 cells, less than Yamanaka’s technique achieved, Thomson says, but still enough to create several cell lines from a single experiment.
　　[F] Scientists have managed to reprogram human skin cells directly into cells that look and act like embryonic stem (ES) cells. The technique makes it possible to generate patient-specific stem cells to study or treat disease without using embryos or oocytes—and therefore could bypass the ethical debates that have plagued the field. “This is like an earthquake for both the science and politics of stem cell research,” says Jesse Reynolds, policy analyst for the Center for Genetics and Society in Oakland, California.
　　[G] Although promising, both techniques share a downside. The retroviruses used to insert the genes could cause tumors in tissues grown from the cells. The crucial next step, everyone agrees, is to find a way to reprogram cells by switching on the genes rather than inserting new copies. The field is moving quickly toward that goal, says stem cell researcher Douglas Melton of Harvard University. “It is not hard to imagine a time when you could add small molecules that would tickle the same networks as these genes” and produce reprogrammed cells without genetic alterations, he says.
(此文选自Science2007年刊)
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Aboard a vessel, multiplying a load’s weight by the distance of the load’s center of gravity from the centerline results in th eload’s（）.

The center of flotation of a vessel is the point in the waterplane（）.

The Medieval era in music is considered by most scholars to begin during the reign of Pope Gregory and to have　　　　　　　　　　　　　　　　　　A　　　　　 B　　　　　　　 Cended around the middle of the 15th century. No error　　　　　　　　　D　　　　　　　　　　　　　　　E

Practice 2　　●You are the secretary of the manager of the Sales Department. A recent decline in sales volume worried the manager deeply and he wanted to hold a meeting to discuss the reasons at 4 p.m. today in the 2nd Meeting Hall.　　●Write a note to all the staff of the Sales Department:　　● informing them of the time, place and content of the meeting,　　● asking them to sum up the reasons before hand,　　● telling them to prepare to discuss in details.　　●Write 30-40 words.

Select the three features common to the majority of switches in the Cisco Small Business portfolio.（）

If the measures of the angles of a triangle are in the ratio of 3: 4: 5, what is the measure of the smallest angle of the triangle?