Professor Smith, along with his assistant, on the project day and night to meet the deadline.
A. work
B. working
C. is working
D. are working
网友回答
A. work
B. working
(答案→)C. is working
D. are working
解析：考查主谓一致。along with连接两个并列主语时，谓语动词和前一个主语保持一致，句子主语是Professor Smith,所以谓语动词用单数形式，选C。