Professor Smith along with his assistants on the project day and night to meet the deadl

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：考查主谓一致。主语与along with 连用时不受其限制，谓语动词应与主语保持一致，题中主语为Professor Smith，所以谓语动词用单数形式，选C。