It is the most severe situation Japanese .
A. that, has faced
B. where, has faced
C. that, have faced
D. where, have faced
网友回答
A. that, has faced
B. where, has faced
(答案→)C. that, have faced
D. where, have faced
解析：考查定语从句和主谓一致。句意：这是日本人曾经面对过的最困难的情况。本句中定语从句的先行词是the most severe situation，使用关系代词that指代先行词在句作为动词face的宾语。Japanese是指日本人，表示的是复数的概念，谓语动词使用复数形式。故C正确。