There is a saying yesterday is history tomorrow is a mystery. But today is gift. That i

问题补充：

There is a saying, yesterday is history, tomorrow is a mystery. But today is gift. That is why it’s called present.

A. /; /

B. the; a

C. /; a

D. a; the

答案：

A. /; /

B. the; a

C. /; a

(答案→)D. a; the

解析：考察冠词用法。根据题意，有一个说法，昨天是历史，明天是一个谜。但是今天是一个礼物。这里是泛指，用不定冠词。那就是他为何被称作今天的原因。这里的present是特指，故用定冠词，选D。