What contribution did al-khwarizmi make to the world of mathematics?
a. he developed the formula and process used to make persian rugs.
b. his work became the basis for algebra.
c. he created the number system based on chinese number system.
d. he determined the formula for finding the hypotenuse of a right triangle.

china unilaterally claims the entire south china sea as sovereign territory, then builds artificial islands to bolster its claim. it suddenly activates an air defense identification zone over the east china sea, and threatens to down any aircraft that does not report its position. it builds roads into indian territory, then redraws the maps to show that it is actually chinese territory. the people's republic under president xi jinping is quickly becoming the bully of asia.

for the united states of america, 1945 to 1964 was a time of high economic growth and general prosperity. it was also a time of confrontation as the capitalist united states and its allies politically opposed the soviet union and other communist countries; the cold war had begun.

explanation: