How much of earth's atmosphere is made up of nitrogen and oxygen?
a. 100 percent
b. between 25 and 75 percent
c. close to 99 percent
d. less than 1 percent

Northeastern china, north korea, northern japan containing coniferous forests, temperate grasslands, and agriculture, are all part of what climate zone? a. tropical desertb. desertc. humid subtropicald. humid continental

How do oceanographers measure the salinity of ocean water?

What does the kyoto protocol aim to reduce