一根粗细均匀的导线，两端加上电压U时，通过导线中的电流强度为I，导线中自由电子定

根据短文内容，从下框的A—F选项中选出能概括每一段主题的最佳选项。选项中有一项为多余选项。

A． How can you select your test location（地址）? B． How many times do you plan to take the test? C． When do you have to hand in your test scores? D． What is the most appropriate test date for you? E． Where do you stand in your high school coursework? F． What are the factors determining your choice of test time?

小题1:
The ACT is offered nationally several times a year, between September and June． However, it's not offered at every test center on each test date． If you need to take the ACT on a day other than Saturday because of religious reasons, you’ll want to be especially attentive in selecting a test date because the non-Saturday dates are less frequent and are held at fewer test centers．
小题2:
One of the first things you should find out, then, is where the ACT is being offered in your area． A quick and easy way to get that information is by accessing ACT's website at www．actstudent．org． Or your high school guidance counselor should be able to give you that information． It's also printed in the booklet Registering for the ACT, which is available free from your school counselor． Often, your own or a neighboring school will serve as a test center．
小题3:
One important decision you need to make is whether you should take the ACT during your junior or your senior year in high school． A number of factors will affect this decision． First, you should find out when colleges you're interested in need to have your test scores． Is there a special program or scholarship for which you want to apply? If so, is there a deadline by which you need to have test scores submitted to the college or agency? Score reports are normally mailed about 3-7 weeks after the test date． Just be sure you're doing everything, including taking the ACT, early enough to keep all your options open．
小题4:
Another consideration in deciding when to take the ACT is where you stand in your high school coursework． If you're in a college-prep program and taking a lot of courses in English, mathematics, and science in your sophomore and junior years, it may be wise for you to take the ACT in your junior year, while those subjects are still fresh in your memory． If, on the other hand, you're studying material covered on the ACT during your senior year, it's reasonable to assume that your performance on the ACT might be better then．
小题5:
Perhaps you'll decide to take the ACT more than once, in hopes of improving your score． In that case, it's probably better to take the exam in your junior year to allow time for a second try． There are several advantages to taking the ACT in your junior year: （i） You probably will have completed much of the coursework corresponding to the material covered on the ACT． （ii）You'll have your ACT scores and other information in time to help make decisions about your final year of high school coursework． （iii） You'll have your ACT scores and information from colleges in time to make decisions about visiting campuses or contacting schools．