We live day by day but in the great things the time of days and weeks so small that a

问题补充：

We live day by day, but in the great things, the time of days and weeks so small that a day is unimportant.

A. is

B. are

C. has been

D. have been

答案：

A. is

B. are

C. has been

D. have been

解析：句子主语为the time，故用谓语要用单数; 再根据句子前后的时态live和is，可知此处宜用一般现在时，不用现在完成时，故选A。