读下图，回答下列各题。

A

    When people say “culture”, we 1art and history. But one very famous symbol in American culture is a cartoon. We all know and love the black mouse

    2two large round ears---Mickey Mouse. Over 80 years ago, he first 3in the cartoon Steamboat Willie. When this cartoon4in New York 5November 18,1928,it was the first cartoon with sound and music. the man behind Mickey was Walt Disney. He became very rich and successful.

为了探究滑动摩擦力大小跟哪些因素有关，小明同学在老师的指导下，做了一系列实验，以下是部分实验步骤（实验过程中，保持长木板水平）．

第1次：把木块平放在长木板上，用弹簧测力计水平拉动木块，（图甲），读出弹簧测力计的示数，并记录下表中．

第2次：把木块侧放在长木板上，用同样的方法拉木块，（图乙），记下相应的示数．  

第3次：把两块相同木块叠在一起平放在长木板上，再用同样的方法拉木块，（图丙），记下相应的示数：