物体做匀加速直线运动，相继经过两段距离为16 m的路程，第一段用时4 s，第二段用时2 s，则物体的加速度是（   ）

    If you are interested in studying at an American university, you have to take the Test of English as a Foreign Language. The test is widely known as the TOEFL. It is the most widely used language exam for American universities.

    There are two major kinds of the TOEFL test. The first is the IBT，or Internet based Test. It is offered in most of the world and accepted by nearly every university and scholarship program in the United States. The other kind of the test is called the Paper­based Test or PBT. The PBT is less costly to take and does not require use of the Internet.

    But how to get started with TOEFL? Here are some tips.

    ⒈Plan ahead — It takes a long time to improve your TOEFL score. Do not expect a big lift in your test results after two weeks. You will have to spend a lot of time and energy.

    ⒉Master the basics first — You should have to be good at basic English before you take the test. If you score below 500 on the PBT or 70 on the IBT, study for a few months and come back to the TOEFL later.

    ⒊Get a study guide — It is easy to find study guides for the IBT. Pearson, Barron's, ETS, and Kaplan all produce quality materials, take a practice test once or twice a month. The best study guides will have explanations in the answer key.

    ⒋Use outside resources — Remember, you are learning a language, not a test. You can improve your TOEFL score by making English part of your daily life. Some simple ways are listening to English speakers, watching movies and reading newspapers. Some others are reading English textbooks, sending and reading text messages in English, and writing online in English.

    The best way to do well on the TOEFL is to know English well. The real goal of the test is to measure how well a student can communicate in English­speaking classroom.

    If you want to know more, please click here.

阅读下面甲乙文言选段，完成后边各题。
       【甲】水陆草木之花，可爱者甚蕃。晋陶渊明独爱菊。自李唐来，世人甚爱牡丹。予独爱莲之出淤泥而不染，濯清涟而不妖，中通外直，不蔓不枝，香远益清，亭亭净植，可远观而不可亵玩焉。
        予谓菊，花之隐逸者也；牡丹，花之富贵者也；莲，花之君子者也。噫！菊之爱，陶后鲜有闻；莲之爱，同予者何人?牡丹之爱，宜乎众矣！
                                                                                                                                                                                                            （节选自周敦颐《爱莲说》）
        【乙】自荷钱出水之日，便为点缀绿波；及其劲叶既生，则又日高日上，日上日妍。有风既作飘摇之态，无风亦呈袅娜之姿,是我于花之未开，先享无穷逸致矣。迨至菡萏成花，娇姿欲滴,后先相继；及花之既谢，乃复蒂下生蓬，蓬中结实，亭亭独立，犹似未开之花，与翠叶并擎，不至白露为霜,而能事不已。此皆言其可目者也。 可鼻则有荷叶之清香，荷花之异馥,避暑而暑为之退，纳凉逐之生。 至其可人之口者，则莲实与藕,皆并列盘餐,而互芬齿颊者也。 只有霜中败叶，零落难堪，似成弃物矣,及摘而藏之，又备经年裹物之用。 是芙蕖者也,无一时一刻，不适耳目之观；无一物一丝,不备家常之用者也。
                                                                                                                                                                                                             （节选自李渔《闲情偶寄》）
       【注释】①荷钱：指初生的小荷叶。②劲叶：指长大了的荷叶。③菡萏：未开的荷花。④异馥：异香。⑤芙蕖：荷花。