Scoria cones are composed primarily of:

A) ejected fragments of vesicular lava
B) blocky lava flows and lahar deposits
C) pahoehoe and/or a'a
D) volcanic ash

What is water scarcity called that occurs due to increasing numbers of people relying on fixed levels of runoff? 

A)  desiccation 
B)  drought 
C)  aridity 
D)  water stress

What is the impact of agriculture on the land? 

A)  It increases soil fertility. 
B)  It increases microorganism diversity. 
C)  It causes soil desalination. 
D)  It causes soil erosion.