等差数列的前项和为30,前项和为100,则它的前项和是( ) A.130 B.170 C.210 D.260 答案:C15.Lost:My school ID card.Its number is 2007712.My name is Mary Brown.Please call me at 695-6385.Found:A schoolbagIs this your schoolbag?It's black and white.My name is Tony Green.My phone number is 236-0731.Cindy:A notebook is in the school library.It is red.Is it yours?Ask the teacher for it.MikeFound:A set of keys.Please call Jane at 498-2456.31.Mary's telephone number isAA.695-6385 B.236-0731 C.2007712 D.498-245632.The schoolbag isCA.green B.white C.black and white D.red33.D found a set of keys.A.Mary B.Tony C.Mike D.Jane34.Tony's last name isBA.Brown B.Green C.Mike D.Miller35.Cindy'sC is in the school library.A.school ID card B.backpack C.notebook D.keys.