为你解答.
You should (B、pay attention to) the teacher in class instead of the noise outside the classroom.
上课时,你应该注意听老师讲,而不是注意教室外的噪声.
解释：pay attention to,注意某事.
take care of是“照看”,stand for是“代表”,look for是“寻找”,意思都不合适.