https://online2.tingclass.net/lesson/shi0529/0001/1240/16-3.mp3
https://image.tingclass.net/statics/js/2012
21. There are few areas of our lives in which tools don't play an ______ part.
A. indispensable B. independent C. indistinguishable D. indiscriminate
<indispensable>
indispensable 不可或缺的，必要的，必不可少的
expense 花費，費用
expenditure 花費
expensive 花費的
</indispensable>
<independent>
independent 不可依靠的，獨立自主的
</independent>
<indistinguishable>
indistinguishable 不能區(qū)分的，不可辨別的，無法辨認的
</indistinguishable>
<indiscriminate>
indiscriminate 不辨善惡的，不辨美丑的
</indiscriminate>
