题目

阅读理解。 April Fool’s Day is a day to play jokes on others. No one knows how this holiday began but it was thought to begin in France. In France, New Year’s Day was celebrated on March 25 and celebrations lasted until April 1st. When New Year’s Day was changed from March 25 to January 1st in the 1560s by King Charles IX （查理九世）, there were some people who still celebrated it on April 1st and those people were called April Fools. April Fool’s Day is a “for-fun-only” day. Nobody is expected to buy gifts or to take their friends out to eat in a fancy restaura15．如图所示，在弹簧测力计下挂一个重力为2N的软铁，软铁下方有一个螺线管，螺线管的两端与金属导轨ab、cd相连，当导线AB 在导轨上分别向左、向右滑动时，弹簧测力计的示数将分别为（　　）A．都大于2NB．大于2N、小于2NC．小于2N、大于2ND．大于2N、等于2N