Miami and Oklahoma City both of were the last two undefeated teams in the NBA this season

问题补充：

Miami and Oklahoma City, both of were the last two undefeated teams in the NBA this season, lost for the first time on January 3rd.

A. whom

B. them

C. which

D. those

答案：

A. whom

B. them

(答案→)C. which

D. those

解析：句意：迈阿密热火队和俄克拉荷马城雷霆队于1月3日首次败北，他们都是NBA这个赛季最后被击败的球队。逗号前后都是句子，所以这里缺少连词，故排除BD；这里是非限制性定语从句，先行词是Miami and Oklahoma City，故选C。