Sun Yat-sen became the first president of China soon after A. Western powers upset the country's internal trade network.
B. Japan invaded Manchuria.
C. Mao Zedong died.
D. a series of revolts forced the emperor to abdicate.

its main object was the establishment of "settlement houses" in poor urban areas, in which volunteer middle-class "settlement workers" would live, hoping to share knowledge and culture with, and alleviate the poverty of, their low-income neighbors.

the steam engine.

the locomotive.

the telephone.

the telegraph.

the internal combustion engine.

the rifle.

ironclad ships.

electricity/light bulb.