What extrusive igneous rock type cooled so quickly that visible crystal grains never grew, and the rock is composed entirely of black silicate glass that easily shatters into sharp, knife-like shards?

(A) Obsidian
(B) Pumice
(C) Scoria
(D) Tuff

Although china’s total economic output, measured by gross domestic product (gdp), is third largest in the world, it is considered a developing nation. what is most likely the most important factor for this designation? a. china’s government spends money on things that do not benefit human development. b. china has a large population, so its gdp per person is only modest. c. china has a strong economy but weak literacy and school attendance rates. d. china’s high rates of disease offset the country's economic gains.