Which situation ends with a result of 0?
A. A stock earns $12 on Monday, but loses $4 each of the next 4 days. What is the change in the stock's value for the week?
B. An ion of potassium is made up of 19 positively charged protons and 18 negatively charged electrons. What is the overall charge of the potassium ion?
C. The depth of a lake increases 6 inches on Monday, but the water level evaporates 2 inches each day for the next 3 days. What is the overall change of depth of the lake?
D. Ahmed spends $5 each day for lunch for 5 days. He earns $30 on Friday mowing his neighbor's lawn. What is the total result of Ahmed's income and expenses?