临床医学研究中的保密原则（） A.欺骗、威胁、利诱进行医学临床实验违反了道德和法律

已知集合A={x|mx²-2x+3=0，m∈R}.

（1）若A是空集，求m的取值范围；

（2）若A中只有一个元素，求m的值；

（3）若A中至多只有一个元素，求m的取值范围.

删除Word中的一张表格，可先选表格中的所有行，然后按DEL键即可（）

女性，49岁，近半年数次发生右上腹疼痛，恶心、呕吐，多为夜间睡眠后发作，并向右肩部放射，检查：肥胖体质，血压110/80mmHg，脉搏90次／分，右上腹轻度压痛，无腹肌紧张。经治疗疼痛未缓解，反而持续性加重，右上腹压痛、反跳痛，腹肌紧张，体温38.5℃，此时可能的诊断为（）

A.急性坏死性胰腺炎

B.十二指肠溃疡穿孔并弥漫性腹膜炎

C.胆总管结石

D.结石性坏疽性胆囊炎

E.胆囊结石进入胆总管并堵塞远端

Harvard University, breaking with a major trend in college admissions, will eliminate its early admissions program next year, with university officials arguing that such programs put low-income and minority applicants at a distinct disadvantage in the competition to get into selective universities.
For three decades Harvard has offered a particular form of early admissions, in which students who are accepted early still have the freedom to go elsewhere. Various forms of early admissions are offered by hundreds of colleges and universities, with many requiring applicants to commit upfront(预先) to attending the university if offered early admission.
The popularity of the procedure grew significantly in the 1990s, as colleges tried to increase their competitive advantage by locking in p candidates early. But at Harvard and many other universities officials have grown concerned about that early admissions present a major obstacle to low-income and working-class students. Such students have also been hurt by steep tuition increases and competition with students from wealthy families who pour thousands of dollars into college consultants and tutoring.
Under binding early admission programs, students have to commit to a college long before they know how much aid they will be offered; whereas students who apply for admission ill the regular cycle are able to compare financial-aid offerings from various colleges before making up their minds in April. Under Harvard’s early admissions program, students do not have to decide until May 1 whether to accept an admission offer. Even so, many potential applicants did not understand the distinction between Harvard’s program and those that require an upfront commitment and were discouraged from applying.
Under Lawrence H.Summers, the Harvard president who left office in June, the university took a number of steps to make itself more accessible to poor and working-class students. The idea of abandoning early admission was developed after Derek Bok became interim president. Early admission will remain in effect in the current academic year, which is already under way.

The procedure of early admission grew popular because it helped colleges to secure the recruitment of ______.

教育科学研究有哪些特点？