Tomplacedthebanknotes，_________thechangeandreceipts，backinthedrawer．
A、morethan设数列 {an} 的前 n 项和为 Sn，则 {an} 等差。
(1) S n4=n 2+2n, n=1,2,3
(2) S n4=n 2+ 2n +1,n=1,2,3
Itisestimatedthat，currently,about50，000speciesbecome_____everyyear．
Inordertolivethekindoflifewewantandtobethepersonwewanttobe，wehavetodomorethanjust________withevents．
Thedestructionofthetwintowers_________shockandangerthroughouttheworld．
The opportunity to explore and play and the encouragement to do so Can ________the performance of many children ．
