Professor Smith along with his assistants on the Project day and night to meet the dead

问题补充：

Professor Smith, along with his assistants, on the Project day and night to meet the deadline.

A. work

B. working

C. is working

D. are working

答案：

A. work

B. working

(答案→)C. is working

D. are working

解析：参考主谓一致。本句的主语是Professor Smith, along with his assistants，谓语动词要和前面的名词Professor Smith保持一致，故使用单数形式，排除AD项。B项不能单独做谓语。句意：史密斯教授和他的助手在夜以继日地做这项工作，以赶上最后期限。故C正确。