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>