Maybe our English teacher---in his office A.is B .are C.be,D

【小蜜翻译】：Maybe our English teacher___in his office
A.is B .are C.be,D am
答案：A
该句意思是“可能我们的英语老师在他的办公室里面”
主语是Our English teacher,我们的英语老师,是一个人,所以应该用单数