What is the main reason why soil erosion can be a problem for people?
O
A. People use soil to block the wind.
O
B. People need soil to build houses.
O
C. People use soil to stop weathering.
O
D. People need soil to grow plants.

Bridget is in science class. her teacher gives her two unknown substances and asks her to determine their relative ph. she places a piece of red litmus paper into both substances. the litmus paper turns purple when she places it into substance i. the litmus paper turns blue when she places it into substance ii. a. substance i is a neutral substance and substance ii is an acid. b. substance i is a neutral substance and substance ii is a base. c. substance i is an acid and substance ii is a base. d. substance i is a base and substance ii is a neutral substance.