16.This is a purely _______ problem, not a political one.

A. additional B. assiduous C. adamant D. academic

<academic>

academic adj.学术的、理论的

</academic>

<additional>

additional 额外的、附加的

additive 添加剂

addendum 补充、附录

adder 蝰蛇

deaf as an adder 充耳不闻

</additional>

<assiduous>

assiduous 勤奋的、好学的

insidious 阴险的、狡诈的

preside (over) 主持

consider 考虑

</assiduous>

<adamant>

adamant 固执的

</adamant>