The problem is sometimes when we are given something on a constant basis we start to ta

问题补充：

The problem is sometimes when we are given something on a constant basis, we start to take them for granted and forget being thankful for what we already have.

A. that

B. how

C. where

D. which

答案：

(答案→)A. that

B. how

C. where

D. which

解析：A 考察名词性从句。主语是The problem，is是系动词，后面接表语从句。从句中有包含有when引导的时间状语从句，由于从句句意通顺，成分完整，应该使用that引导，that不充当成分，只做引导词。故A正确。