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在“探究小车速度随时间变化的规律”的实验中：1.实验室提供了以下器材：打点计时器、一端装有定滑轮的长木板、小车、纸带、细绳、钩码、刻度尺、交流电源、弹簧测力计。其中在本实验中不需要的器材是__________________。2.已知打点计时器所用交流电的频率为50Hz。如图所示为实验所打出的一段纸带，在顺次打出的点中，从O点开始每5个打点间隔取1个计数点，分别记为A、B、C、D。相邻计数点间的距离已在图中标出，则打点计时器打下计数点C时，Saying goodbye to friends who are moving away is always hard. A Going-away Party can help to make everyone’s spirits bright and let your friends know how much you will miss them. We also have several other kinds of party invitations that my be suitable for a Going-away Party.Invitation to a Going-away PartyThursday, 19th MarchDear Joy and Mary,You are invited to a farewell for the “GREEN FAMILY’S VISIT TO AFRICA”Departure (启程) date: 4th MayThe best part of our big adventure to Africa will be when we come face-to-face with elephants, lions, crocodiles and other African wildlife. We have always wanted to do this.Party given by: Mr and Mrs Green, Tom and JohnDate: Saturday, 11th April 2013Time: 5:00 p.m. to 10:00 p.m.Place: 29 King Street, New Town, SydneyReply by: Thursday, 2nd AprilPhone: 6458515Food and drinks will be prepared at the party.P.S. This event is NOT to be missed! We hope to see you there! 小题1:Who is the invitation sent to?A．Mr and Mrs Green.B．Joy and MaryC．Tom and John.D．Joy and John.小题2:The party will take place on          .A．19th MarchB．4th MayC．2nd AprilD．11th April小题3:The Greens will go to Africa to          .A．see some old friendsB．have a Going-away PartyC．see some African wildlife D．buy some food and drinks