这里用的是部分倒装的结构.
当never,hardly,seldom,little,few,not until,not,no,no sooner,by no means,under no circumstances等否定词置于句首时,其后要用部分倒装.如：
Never did I see him again.后来我再也没见到过他了.
Little did I dream that the girl was my niece.我做梦也没想到那女孩是我的侄女.
后面的句子用部分倒装,即将主语与助动词倒置,其结构与一般疑问句大致相同
little不是主语.主语还是they,they know little when……是正常的语序.
that是引导定语从句