The correct answer is - Algebra.
The Muslim Caliphates managed to get hold on to lots of works and inventions from the civilizations before them, so they had a lot of material to learn and develop. One of the things that caught their eye the most was the math, and they kind of became obsessed with it. Lots of scholars were becoming mathematicians, and they were giving it special attention, and over time, from the dedication from it, a new innovation came through, the algebra.