because her mum believes that is a good habit ——（learn）the knowledge

because her mum believes that is a good habit ——（learn）the knowledge
because her mum believes that is a good habit ——（learn）the knowledge

because her mum believes that is a good habit ——（learn）the knowledge
to learn
a good habit to do sth
一个.的好习惯

不缺句子成分，所以可能缺定语，动词不定式做定语，to learn

他的速度提升员工需要多少土豆丝