Select the correct answer from each drop-down menu. Complete the passage about atmospheric carbon dioxide. A warming global climate can create hot and dry regions. It can also contribute to natural CO2 emissions. For example, lightning strikes in a dry forest region can cause . The added CO2 from this event results in a positive feedback loop, increasing heat in the atmosphere as it .

1. A. Valcanoes
B. Wildfires
C. Acid Rain

2. A. Supports Photosynthesis
B. Magnifies the Green House Effect
C. Escapes to Space

Use your vocabulary words to complete the sentences below. more of the world's population is now concentrated in heavily populated urban areas known as a this is quite a contrast from the past when or native groups were either farmers or — hunters and gatherers who moved between places in search of food. advanced technology has led to the integration of world economics and cultures, in the world's more developed countries. this integration requires , the responsible use and management of natural resources.

Given: circle a externally tangent to circle b. how many possible common tangents to circles a and b can exist? 2 3 4

Where does the availability of water pose the greatest problem