In my opinion life in the twenty-first century is much easier than .A. that used to beB. i

问题补充：

In my opinion,life in the twenty-first century is much easier than .

A. that used to be

B. it is used to

C. it was used to

D. it used to be

答案：

A. that used to be

B. it is used to

C. it was used to

(答案→)D. it used to be

解析：(than)it used to be是比较状语从句，it指上文中的life，used to be表示“过去是”。根据所提供的情景“life in the twenty-first century is much easier than”可判断出表示“以我看来，21世纪的生活比过去容易”。be used to后接动词+ing形式作宾语，表示“习惯于”，其主语一般是表示“人”的名词或代词。