Which if the following are the two primary gasses found in the earths atmosphere

•nitrogen and oxygen
•nitrogen and carbon
•hydrogen and carbon
•carbon and helium

Which of these is a drawback of using natural gas? a. it is fairly safe for use in homes.b. it burns more cleanly than crude oil products.c. scientists have developed new ways of extracting it.d. during its extraction, groundwater can be contaminated.

The desert expands by hundreds of square miles each year.

The creation of the european union has had all of the following effects except