My mother very busy weekends. A. does usually; at B. is usually; on C. usually is; on

问题补充：

My mother very busy weekends.

A. does usually; at B. is usually; on C. usually is; on

答案：

解析：本题考查频率副词usually的位置和短语on weekends的使用。本题的含义为我的母亲在周末通常非常的忙，副词通常usually位于be动词之后，在周末使用固定短语on weekends，故本题选B。