It's Charlie's birthday today, but he isn't feeling happy. No one wishes him a happy birthday. Mother says nothing about his birthday. She just tells Charlie to play outside. At lunchtime, his mother calls, "Come in for lunch, Charlie!" Charlie slowly walks into his house. But the living room looks different. Charlie sees a big "Happy Birthday"banner(横幅). Then, he sees a birthday cake, balloons, presents, and all of his friends. "Happy birthday!" everyone shouts. Charlie’s face lights up. He is happy and surprised(吃惊). No one forgets his birthday after all!

如图所示，放在水平桌面上的木块A处于静止状态，所挂的砝码和托盘的总质量为0.6kg，弹簧测力计读数为2N，滑轮摩擦不计．若轻轻取走盘中的部分砝码，使总质量减少到0.3kg，将会出现的情况是（g=10m/s²）（   ）