如图甲所示的地面清洁机器人，质量为3kg，要求对水平地面压强不超过3000Pa，机器人在水平地面运动时，所受推力与速度关系如图乙所示.求：

老师讲了“固体的密度”这节知识后，小楠对冬季出产的红萝卜的密度感兴趣了．他找了一个小红萝卜，决定想办法测出它的密度．

已知函数f_k（x）=a^x+ka^﹣x，（k∈Z，a＞0且a≠1）．

（Ⅰ）若f₁（1）=3，求f₁（ $\frac{1}{2}$ ）的值；

（Ⅱ）若f_k（x）为定义在R上的奇函数，且a＞1，是否存在实数λ，使得f_k（cos2x）+f_k（2λsinx﹣5）＜0对任意x∈0， $\frac{2\pi }{3}$ 恒成立，若存在，请求出实数k的取值范围；若不存在，请说明理由．

阅读理解
    John and Mary had a nice home and two lovely children. John had just been asked to go on a business trip to another city for several days and Mary would go with him too. They hired a reliable woman to care for their children and returned home a little earlier than they had planned.
    As they drove into their hometown, they found a home on fire. After having a look, Mary said, “Oh well, it isn't our fire. Let's go home.” But John drove closer and said, “That home belongs to Fred Jones who wouldn't be off work yet. Maybe there is something we could do.”
    John noticed an old lady screamed to him, “A children! Get the children!” John grabbed (抓住) her by the shoulder saying, “Get a hold of yourself and tell us where the children are!” “In the basement,” cried the lady.
    In spite of Mary's disagreement, John soaked (浸湿) his clothes and ran to the basement which was full of smoke. He found the door and grabbed two children. As he left he could hear some more cry. He sent the two badly frightened children into the waiting room and asked how many more children were down there. The told him two more and Mary grabbed his arm and screamed, “John! Don't go back! It's dangerous! That house will fall down in any second!”
    But he shook her off and went back. It seemed a very long time before he found both children and started back. As he climbed up the endless steps the thought went through his mind that there was something strangely familiar about the little bodies next to him, and at last when they came out into the sunlight and fresh air, he found that he had just rescued his own children. The baby-sitter had left them at this home while she did some shopping.

根据短文理解，从A、B、C、D四个选项中选择最佳答案填空。

    Do you think of your parents? "Yes, of course," you may answer, "I buy a present for my mother on 1. And I give my father a present on Father's Day, 2. "Then what about the other days of a year? Always 3 to think of your parents, not just on some important days.

    I have a friend who 4 alone, because her parents live in another city. One day I went to see her. We had a nice chat. Then she wanted to make a 5. She dialed the number, but then she put the phone 6. After about ten seconds, she dialed the number again, "Hi, Mum……"

    Later I asked, "Why did you dial the number 7?" She smiled, "My parents are old. They can't get close to the telephone 8. I always do so when I call them. I just want to give them 9 time to answer the call."

    My friend is a good girl. She is always 10 her parents. You also want to be a good child, right? So why not learn from her?