问题 选择题

甲醛是室内装潢时的主要污染物之一,它的化学式为CH2O,下列说法正确的是(  )

A.甲醛是由碳原子和水分子构成的

B.甲醛分子由碳原子、氢气分子、氧原子构成

C.甲醛是由碳、氢、氧三种元素组成的物质

D.甲醛是由1个碳元素、2个氢元素、1个氧元素组成的物质

答案

A、甲醛是由甲醛分子构成的,它不存在水分子,故A错误;

B、甲醛分子由碳原子、氢原子、氧原子构成,甲醛分子中不存在氢分子,故B错误;

C、甲醛属于一种物质可以用元素来解释,甲醛是由碳、氢、氧三种元素组成的物质,故C正确;

D、元素属于宏观概念不能论个数,故D错误.

故选C.

填空题

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.

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