在正方体ABCD﹣A₁B₁C₁D₁中，下列各 式运算结果为向量$\overrightarrow{B{D}_1}$的是（　　）

①（$\overrightarrow{A_1{D}_1}$﹣$\overrightarrow{A_{1}A}$）﹣$\overrightarrow{AB}$；   

②（$\overrightarrow{BC}$+$\overrightarrow{B{B}_1}$）﹣$\overrightarrow{D_1{C}_1}$；

③（$\overrightarrow{AD}$﹣$\overrightarrow{AB}$）﹣$\overrightarrow{D{D}_1}$； 

④（$\overrightarrow{B_1{D}_1}$﹣$\overrightarrow{A_{1}A}$）+$\overrightarrow{D{D}_1}$．

    Your mouth will be opened and your teeth will be shown when you laugh. However, the h____ those teeth are, the happier you look. Strong, healthy teeth can help you eat the right food to help you g____ . They also help you speak clearly. But do you know how to take care of your teeth? These should be f____ .
    Brush your teeth twice a day after breakfast and before bedtime. If you can, brush after lunch or after eating sweet cakes. T____  your time while brushing. Spend at least 3 minutes each time you brush. Brush all of your teeth, not just the f____ ones. Spend some time on the teeth along the s____  and in the back.  
B    e sure the t____  you use is soft and should be changed every three months or even less.
Learn how to floss(用牙线清理) your teeth, which is a very important way to keep them healthy. It feels s when you do it at first, but soon you'll get used to doing it. The floss cleans up food that's h____  between your teeth.
    Brushing and flossing keep your teeth healthy. You also need to c____  about what you eat and drink. Eat lots of fruits and vegetables and drink water i____  of drinks.

任务型阅读。认真阅读下列短文，并根据所读内容在文章后表格中的空格里填入一个最恰当的单词。每个空格只填1个单词。

    Time management refers to managing time effectively so that the right time is allocated to the right activity. Time management is essential in every field of life because time is the precious resource one needs to accomplish a task. Every single moment that passes once will never come back again. Time management helps you do your task in time and use your time more productively. It helps you to identify the useless activities which can be avoided and how time can be saved. It helps you allocate proper time for a task and perform the task more efficiently.

    A student's daily routine is filled with a lot of activities. Some are related to his studies, some are essential for his life and some are for entertainment or physical fitness. Still some activities have no use and just waste time. Similarly if the number of the activities for entertainment exceeds what is reasonable, they waste the time of a student. These activities include using the internet for chatting, playing games, watching movies or listening to music for hours on end. Such activities are called “distracters” which distract one from one's real purpose.

    Games and physical exercise are important for a student because they keep him fit in body and mind but game time should be controlled as it may waste his time.

    No one wastes time intentionally. Time is always wasted in an insensible way. That's why a student is aware of it until the days of exams come. So it is better to use the present time more effectively than cry over what you've done in the future.

    As for a student, time management compromises various steps. It is not only necessary to allocate time for different subjects but also to identify right time for each such subject. What's more, to identify the distracters which become causes of wastage of time is of significance as well.

    Take a pen and sheet. Write down all the activities you do in your daily routine. Calculate how much time you have for your studies other than other activities. Determine how much time a subject can take out of your total study time. See which subject need more time.

Time management