Q. Deborah Aguiar-Velez, founder of sistemas corporation, has written a computer textbook in Spanish for people who speak Spanish and so then do not have to rely on translations from English.

A. for people who speak Spanish and so then
B. for people who speak Spanish, and then they
C. for people speaking Spanish who
D. so that people who speak Spanish
E. so that people can speak Spanish and then.

Could some one explain why the answer is "D".

Is this kind of question a Subject-Verb Agreement one? or a IDIOMS one?