The Ching Ming Festival or Grave-Sweeping Day falls on April 4 this year is an importan

问题补充：

The Ching Ming Festival or Grave-Sweeping Day, falls on April 4 this year, is an important date in the Chinese calendar

A. which B that C. what D. where

答案：

解析：考查定语从句。从句中缺少主语，所以排除D项，而what不能引导定语从句，that不能引导非限制性定语从句，所以A项正确。