8. One pervasive theory explains the introduction of breakfast cereals in the early 1900s as a result of the growing number of automobiles, which led to a decline in horse ownership and a subsequent grain glut; by persuading people to eat what had previously been horse feed, market equilibrium was restored.
(A) by persuading people to eat what had previously been horse feed, market equilibrium was restored
(B) persuading people to eat what had previously been horse feed restored market equilibrium
(C) by persuading people to eat what had previously been horse feed, it restored market equilibrium
(D) the persuasion of people to eat what had previously been horse feed restored market equilibrium（B）
(E) market equilibrium was restored when people were persuaded to eat former horse feed
why b？ | 
