Which of the following best describes why estuaries are important resources? A. They are the world's richest sources of precious metals. B. They are among the most productive types of ecosystems. C. They prevent weathering of rock from slopes and cliffs. D. They help stabilize the global climate.

On a spring day, a middle-latitude city (about 40? north latitude) has a surface (sea-level) temperature of 10 ? c. if vertical soundings reveal a nearly constant environmental lapse rate of 6.5 ? c per kilometer and a temperature at the tropopause of –55 ? c, what is the height of the tropopause?