To her joy Della earned first the trust of her students and then of her colleagues. A.

问题补充：

To her joy, Della earned first the trust of her students and then of her colleagues.

A. that

B. one

C. ones

D. those

答案：

(答案→)A. that

B. one

C. ones

D. those

解析：

试题分析:句意：使她高兴的是，黛拉首先赢得了学生们的信任，然后又赢得了她同事的信任。that指代不可数名词；one指代单数可数名词；ones指代复数名词，是泛指概念；those指代复数名词，是特指概念。此句中被替代词trust是不可数名词，故答案选A.。