The original purpose was to <span>identify areas of academic weakness in grade school children.
By knowing this areas of academic weakness, the education establishment could develop a better curriculum that would aid the students in tackling these academic subjects.</span>
I believe the answer is: A just-noticeable difference
In painting, A just-noticeable difference refers to the amount of things that needed to be change for a difference to be noticeable.
The threshold usually depended on the type of audience that being aimed toward, (for common audience, the threshold of differences would be relatively higher compared to expert audience)<span />
C) Textiles industry was the first mechanized industry.
