大是大非
major issue of right or wrong;major issue of yes or no; huge stake; cardinal question of right and wrong
中国在这个～的问题上决不含糊。Given the stakes involved in this issue. China will not yield any ground(or has no room for flexibility).
大是大非dà shì dà fēi
属于政治原则性的是非问题。major issues of principle, cardinal questions of right and wrong, an issue of principle, a matter of principle, right and wrong on issues of major importance