（）是最根本的思维方法，是研究各类方法的理论基础和指导思想，对一切科学具有最普遍的指

A couple weeks before he was scheduled to have his teeth cleaned, Gerald Zember. felt a slight pain in the back of his mouth. The retired lawyer figured he had burnt his tongue sipping hot soup or developed an ulcer from one too many spicy meals. And at first glance, Zember’s Ft. Lauder- dale, Fla., dentist, William Balanoff, didn’t notice anything unusual during a routine examination-until he pulled out a new oral-cancer screening tool called ViziLite.

According to the passage, the lesion Balanoff found was _________.
A. usually caused by excessive smoking
B. an obvious case of cancer sores
C. a cancer lump
D. leading Zember to death

After Zember rinsed with a raspberry-flavored acetic solution, Balanoff inserted a ViziLite light stick into his patient’s mouth. Suddenly, a tiny white lesion became visible on the side of Zember’s tongue. "It was tiny, but I couldn’t explain it away," says Balanoff, since Zember had no history of canker sores that could have left such a mark. Zember, 78, did have a history of smoking, though, which put him at higher risk for oral cancer. So Balanoff referred him to an oral surgeon to have the lesion checked out. A biopsy revealed the cells were cancerous. "It was so tiny, I might not have noticed it until a year or a year and a half later [once it had grown]," says Balanoff. "By then, it would have been a stage-three cancer, and his chances wouldn’t have been that good."About 30,000 Americans will be diagnosed with oral or pharyngeal cancer this year, and more than 8,000 people will die from it. The death rate--about 50 percent over five years--hasn’t changed much in the past few decades, in part because the cancer often isn’t detected until it’s visible to the naked eye. "Probably about two thirds of the cases at the time of diagnosis and treatment are already at an advanced stage," says Sol Silverman, a professor of oral medicine at the University of California, San Francisco, and an oral-cancer spokesman for the American Dental Association. "So what can we do today Early detection."
Over the past few years, the American Dental Association has made detecting oral cancer earlier a priority, launching an awareness campaign in 1999. But it’s taken a little while for the new screening tools to catch on. ViziLite, manufactured by Phoenix--based Zila Pharmaceuticals, was approved by the Food and Drug Administration in November 2001, but not widely marketed until this year. Another device, OralCDx’s oral-brush biopsy, which uses a specialized brush to collect several test ceils from the tongue’s surface, has been available since 2000. But it was only this year that Delta Dental Plan of Michigan and its affiliated plans in Ohio and Indiana became one of the nation’s first dental benefits providers to include the diagnostic tool, distributed by Sullivan-Schein Dental, as part of its standard benefits ( DaimlerChrysler was the first employer group to incorporate the benefit for it’s 400,000 union workers).
Soon there may be another option, too. Zila’s OraTest, a patented five-minute mouth rinse that uses a special dye, has already been approved for use in more than a dozen other countries, but still awaits approval from the FDA.

Fe、CO 、CuO 、NaOH溶液 、Na₂CO₃溶液 、Ba(OH)₂溶液 、稀H₂SO₄七种物质，在常温下两种物质间能发生的化学反应有[ ]

A. 4个

B. 5个

C. 6个

D.7个

在建筑工程中常用的树种中的针叶树类可分为（）类。

A、4

B、6

C、8

D、10

梁奶奶今年已经75岁了，梁奶奶的老伴在十年前去世。梁奶奶生有两儿一女，现与大儿子一起生活。大儿子在工厂上班，生活十分困难，小儿子自小患有智障，生活不能自理，也由大儿子照顾。女儿的丈夫是某公司的部门经理，生活富裕。梁奶奶要求女儿承担赡养义务，但遭到女儿拒绝。下列关于梁奶奶的赡养的问题说法正确的是( )。

A．赡养老人是儿子的责任，女儿无须承担赡养义务
B．女儿应该承担赡养义务
C．已出嫁的女儿可以不承担赡养义务
D．女儿如不继承老人遗产，可不承担赡养义务

进行操作过程中，遇有开关跳闸时，应（）。