kathy is a teacher,__is clear from her manner.(as)为什么不填all that?

后面是一个从句, 如果用all that 这前面需要有一个连词

as是后面句子的表语

From her manner, it is clear that Kathy is a teacher.
从她的行为举止可以很清楚地看出凯西是一位教师