you should ( )the teacher in class instead of the noise outs

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.