题目

 Our kind teacher wanted to teach us _______ he knew at his lesson. A. that                     B. what                       C. how                       D. which 答案：B  2．若a≠b,数列a,x1,x 2 ,b和数列a,y1 ,y2 ,b都是等差数列，则           （   ） A．                    B．              C．1                     D．