发光二极管只允许电流从二极管的正极流入，负极流出．小明设计了如图所示的装置，使线圈沿水平方向左右移动，此时会看见两只发光二极管 ____，该装置发光根据的是 ____原理

一米长的绳子，第一次用去 $\frac{3}{10}$ 米，第二次用去这根绳子的 $\frac{3}{10}$ ，两次用的绳子相比（  ）

    “A friend walks in when the rest of the world walks out.” Sometimes in life, you find a special friend:

    Someone who changes your1 just by being part of it;

    Someone who makes you laugh until you can't 2;

    Someone who makes you believe that there really is 3 in the world;

    Someone who convinces(使相信) you that there really in an 4 door just waiting for you to open it.

    This is Forever(永远的) Friendship.

    When you're 5, and the world seems dark and empty, you forever friend 6 you up in spirits and makes that dark and empty world suddenly seem bright and 7.

    You forever friend gets you 8 the hard times and the sad times. If you turn and walk away, your forever friend 9. If you lose your way, your forever friend guide (引导) you, encourages(鼓励)you, holds your 10 and tells you that everything is going to be OK.

    And if you 11 such a friend, you feel happy, because you 12 not worry. You have a forever friend for life, and forever has no 13.

    A true friend is someone who gives you a hand and touches your heart.

    Remember: 14 happens, happens for a reason.

    How many people have eight true friends in fact? Hardly 15 I Know. But some of us have all right friends and good friends.