Which of the following is an example of a positive feedback loop?

a) you feel hungry, so you eat a sandwich. after eating the sandwich, you are no longer hungry, so you decide to pass on dessert

b) sasha sprays pesticide on her garden. the pesticide keeps bugs away and also kills the worms in the soil.

c) john earns one point every times he makes a basket during basketball practice. he practices at home to get better so he can earn more points.

d) a municipal government offers a tax credit to any company that reduces its greenhouse gas emissions by 10% over one year.