In my opinion, life in the twenty-first century is much easier than .
A. what used to be
B. that it used to be
C. it used to be
D. what it used to be
网友回答
A. what used to be
B. that it used to be
C. it used to be
(答案→)D. what it used to be
解析：考查宾语从句。used to do“过去（常常）”；be缺少表语，用what；句意“在我看来，21世纪的生活比过去的生活容易的多。”。故选D。