车内发生火情时，如何及时有效地阻止火势蔓延，____，成为产业界日渐重视的问题。上海化工研究院科研人员研制的无卤阻燃剂产品可以解决这个问题。无卤阻燃剂材料在燃烧时会形成一个泡沫状的碳层，从而阻止火和氧气的接触，____。该材料在燃烧时发烟量少，也不产生有毒和腐蚀性的气体，____。

课外阅读。

                                                                                                  可爱的小白

       我家养了一只可爱的小猫——小白。

       小白长得很可爱。瞧，它全身雪白雪白，摸起来毛茸茸的，十分舒服，仿佛一件白色的貂皮大衣。小白的耳朵可称得上“顺风耳”：一有风吹草动，它很快就瞄准目标。小白的眼睛圆溜溜、水汪汪的。它的胡须又细又长，酷似几根软针。小白的腿又细又长，爪子很尖，脚下有一块肉垫子，走起路来一点声音也听不见。小白的尾巴不粗不细，时而垂在地上，时而摇来摇去，活像一条活蹦乱跳的小白蛇。

      小白不光长得可爱，行动也非常可爱。每次吃饭时，它总是先闻闻，再用脚摸摸，然后，它才会安心地吃。吃食前，它真有绅士风度，可吃起来却很不雅，它很挑食，专拣有腥味的海鲜吃，其他的食物难得一碰。休息时，小白总是喜欢先挑一个好地方，然后，蜷起身子，呼呼大睡。有一次，它竟然钻进了我的被窝里，蒙头大睡，我一进被窝，它喵喵叫，吓了我一跳。

      可爱的小白抓老鼠的时候真是沉着勇敢，尽职尽责。如果它发现老鼠的踪影，就会守候在鼠洞旁，纹丝不动。老鼠只要一出现，它就会奋勇向前，身体一跃按住老鼠，用锋利的牙齿咬住老鼠的喉咙，决不给老鼠喘息反搏的机会，一眨眼的工夫老鼠就一命呜呼了。

小白就是这样一个乖巧可爱的小动物，我十分喜欢它。

完形填空

    My husband Jeff and I moved into our new home in Scottsbluff last year just before Christmas. I did not have the 1 or energy to carry out my traditional Christmas decorating and baking activities. What was the point, anyway? It was going to be a 2 Christmas after all.

    3, the neighborly nature of west Nebraska residents started to trickle (陆续来临) in.

    There was a 4on the door one evening. It was Jeff's new colleague, John Smith, and his wife, Phyllis. The Smiths had stopped by to 5 us with a loaf of homemade bread. They pointed out a 6 on the porch (门廊). Apparently the doorbell wasn't working in the cold snowy weather and we had 7 a visit from the Browns, our across-the-street neighbors, who brought us a Christmas card and more Christmas cookies.

    The 8 feelings brought by these thoughtful gestures lasted longer than the food.

    As Jeff and I were9 pre-Christmas snow from our driveway, Ernie Guzman came over from next door to 10 us to dig out.

    Then, we received an invitation to 11 a Christmas Eve meal with our neighbors, Ernie and Nancy Sommer, and their 12—a 90-year-old lady, who also had no family in the immediate area with whom to spend the holiday.

    Our Christmas Eve was quite merry, thanks to our 13. Our Christmas morning 14 was special, thanks to the Smiths' gift of bread. I was so 15 for these gestures of welcome, especially during the holidays.

    This year, we were again unable to be with our families for Christmas. The 16 and work schedules just made things too difficult. 17 that sense of Christmas isolation (孤立) all too well, we decided to try to round up some other folks who were 18 in the holidays.

    Lonely people are all around us, but most of us 19 notice them. Just take a look around you. Sometimes, the smallest 20 gesture can make a world of difference.

如图所示为电流与电压的关系图像，由此可以判断（  ）