it is generally considered unwise________ parents give a child whatever he or she wants.A why B that C if D howif为什么不行?如果一定要用if,该怎么改

这个是固定句式
it is considered + adj+ to do / doing / that
it充当形式主语,that parents .she wants这一个分句才是真正主语
正语序是That parents.she wants is generally considered unwise.
但是主语太长,就放到后面了
要用if的话应该这样改
A parent is generally considered unwise if he or she gives a child whatever he or she wants.