When you live in a seasonal environment, you can learn that both outdoor and indoor activities have their place. As the seasons1 so does your mood. Certain activities become more or less attractive2 the weather and the length of the day.

    Spring is a time of the year when the world starts to3 from its winter sleep. During this season, I enjoy going on long walks through parks and watching the world come4.

    Many consider summer to be the top of the year. The city comes into full swing5 the weather becomes warmer and warmer. During the summer, I prefer to spend the daytime anywhere that is air-conditioned. This 6include the library, a shopping center or a movie theater. I often enjoy spending the7evenings sitting on the wide balcony of my house and having drinks with my friends.

    Fall, with the8 of the leaves and the summer heat gradually 9is probably another 10 time to go on long walks during the day. I love to be 11during fall and see the life of the city returning to its hibernation (冬眠). Another12to go outside during autumn is to 13the last days of warmth until the next year.

    Winter14 the shortening of days and cooler weather. Outdoor activities tend to become less 15 and sinking down on the sofa with a good book becomes my16 activity. It is not enjoyable to spend time outside if it is too 17I only choose to go outside when I want to go skiing.

    So, my 18to spend time indoors or outdoors is vastly dependent on the19. Different seasons 20different activities and therefore it is Impossible to choose whether I would spend all of my spare time indoors or outdoors.

图是美国大众性期刊《时代周刊》1972年某期的一幅封面画，画中文字意为“为了和平去北京”，画中的两个人物分别是美国总统尼克松和国务卿基辛格。对此封面画所含历史背景信息说明正确的是

某学校新建一座图书馆，较适用于用图书的灭火器材是（　　）

在$△ABC$中，a,b,c分别为角A,B,C的对边，若$A=\frac{\mathrm{\pi }}{3},b=1$,$△ABC$的面积为$\frac{\sqrt{3}}{2}$，则a的值为（   ）