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
A、条件（1）充分，但条件（2）不充分A
等差数列的前n项和公式为Sn=An2+Bn，A、B为全体实数，因此条件(1)充分，条件(2)不充分，选A。
John says that his present job does not provide him with enough ______for his organizing ability.
Theteamplayedhardbecausethechampionshipofthestatewas______.
设圆 C 与圆 (x-5) 2+y2=2 ，关于 y=2x 时称，则圆 C 方程为 ( )
About 20 of the passengers who were injured in a plane crash are said to be in_____condition ．
Tomplacedthebanknotes，_________thechangeandreceipts，backinthedrawer．
