题目

—Thank you for your assistance, without ___I might have been in danger. —That's all right, anyone in my place ________ the same thing. A . that; will do B . it, would C . which; can have done D . which; would have done 答案：D小李等同学“探究声音产生”的装置如图所示，将系在细线上的乒乓球靠近音叉．(1)当小李同学用小锤敲击音叉时，既能听到音叉发出的声音，又能观察到____，通过实验现象得出的结论是____．(2)乒乓球在实验中起什么作用？答：____，便于观察，这种方法叫做___(填“等效法”“控制变量法”“转换法”或“类比法”)．(3)若实验过程中小李同学加大敲击音叉的力度：①听到和看到的现象会有什么变化？答：__________．②根据实验现象的变化，你又总结出什么结论？答：___________．