有机磷农药中毒主要毒作用机制为（）A、抑制胆碱酯酶活性 B、肝损伤 C、肾损伤 D、血液毒

Though hardly as unwelcome as death or taxes, college entrance exams are just as inevitable and almost as dreaded by high school students.
As the testing dates loom for juniors and seniors for the SAT (formerly called the Scholastic Assessment Test) and the American College Test, or ACT, most students are looking for an edge, any edge, in the competition.
And as the number of homes with computers continues to rise, test publishers and software developers have been quick to recognize a growing niche. With the market for test preparation materials at all levels estimated at $540 million annually, they have jumped on the tech bandwagon to produce computerized tutorials that promise to boost scores.
(41) " We believe that it’s important for a student to be prepared to take the tests, " notes Don Powers, a research scientist at the Educational Testing Service in Princeton, N. J. , the organization that administers the SAT for the College Board. " It’s important to know how to take the test so that you won’t get a score that’s lower than you deserve. " But, he adds, " none of the rigorous scientific evidence that we have seen supports these promises" to raise test scores.
(42)Several points, however, do weigh in favor of software as opposed to traditional test-preparation. Cost is a big one.
(43)Convenience is another, as the College Board points out in touting its new sofware.
A few points to remember when evaluating various test-prep software packages:
(44)The exams, though they may seem mystical to the test taker, are not magic and certainly not random. There is little variation in the strategies the programs use to boost test scores because there is little variation in how the test are developed.
Largely, what differentiates one program from another is the computer interface, which can make the software more—or less—user-friendly, and such features as automated tracking of student progress.
(45)A crash course with test prep software is never an alternative to careful, long-term preparation for taking the exams. Some students are better equipped to respond to the self-paced, self-motivated approach software offers than others, Powers notes.
Although parents may be in the market for what they consider " serious " study aids, their children, who are the ones taking the tests, may appreciate the programs that offer a little humor.
Finally, as programs frequently point out, the SAT and ACT, while important to college admissions officers, are only one element of a successful college application.
[A] A test prep course with a live instructor can cost as much as $700. Test-prep software costs $30 to $80.
[B] Most of the programs, in fact, emphasize the importance of " guessing strategies " and eliminating unlikely answers to improve scores. Many students often succeed in exams in this way.
[C] Unlike many programs, this one can give you a quick, easy and comfortable way to achieve a high score. Such programs can turn your dream passing exams into reality.
[D] " I would rather use the program than take a preparation course, because I could do this on my own time and in my own home, " notes one student in the College Board materials.
[E] Although at least one of the test programs asks you how long you have to prepare to take the examination in order to customize the learning curve, all recommend spending a period of weeks, not hours, using the software.
[F] But though many programs offer money-back guarantees, professional test writers tend to scoff at those claims. In their mind, such programs overemphasize its functions.
[G] SAT and ACT is popular with the international students, especially Asian students. Many Asian students chase their dream through SAT and ACT.

对于线性回归，在因变量的总离差平方和中，如果回归平方和所占比例越大，那么两个变量之间相关程度越（）

一I’d like to find a part-time job in the restaurant．

一Good idea．In my opinion，        it doesn’t affect your studies．

A．unless

B．now that

C．even if

D．as long as

高原现象

自耦变压器初级绕组的一部分兼做次级绕组。