Either Sam or Tom an exam at the moment. A. are having B. is having C. were having

问题补充：

Either Sam or Tom an exam at the moment.

A. are having B. is having C. were having

答案：

解析：在either…or句型中，谓语用就近原则，再根据at the moment 表示此刻是现在进行时时态的标志，故选B