The professor came into the classroom, .
A. book under arm
B. a book under arm
C. book under an arm
D. with book under the arm
网友回答
(答案→)A. book under arm
B. a book under arm
C. book under an arm
D. with book under the arm
解析：在独立主格结构中，如使用with复合结构，名词前要用冠词或物主代词。