the studengts are encouraged to read such books________good for them in forming good habits.这里为什么填as are 而不是as they are?

问题描述:

the studengts are encouraged to read such books________good for them in forming good habits.
这里为什么填as are
而不是as they are?

such +名词+as这个结构是定语从句,as这里是关系代词代替先行词books