【单选题】以下哪一个选项不是产生产品纠纷的主要原因:( )。
【简答题】已知数列{a n }满足a 1 =1, a n + a n+1 = ( 1 3 ) n (n∈ N * ) ,S n =a 1 +3?a 2 +3 2 ?a 3 +…+3 n-1 ?a n ,则4S n -3 n a n =______.
【简答题】Since he was born with a silver spoon in his mouth, he spent money like water.
【判断题】定理的充分性证明需要较长的篇幅,在此从略。