孔子在水边感叹时光的流逝，写下“逝者如斯夫，不舍昼夜”的名句，李白也在《将进酒》中用“君不见____，____”表达了人生短促的感慨。

如图所示，用50N的水平拉力F拉着物体在2s内沿水平方向前进了4m，下列说法正确的是（　　）

    Some friends are playing hide-and-seek (捉迷藏) at Mr. Green’ home. They play in Mike’s room. It’s time for Lily to find her friends. Lily first finds Sally.Sally is behind the door. Then, Lily sees Bob. Bob is under the table. Mike is under the table, too. Now it’s time to find David and John. David’s hat is on the sofa. Is David under the sofa? No, he isn’t.John’s schoolbag is on the chair, but he isn’t there.“Where are they?”Lily thinks.Shh! Don’t let her know. They are under the bed!