Analysis of test questions: With the increase of pork price, the profit of raising pigs, the profit of pig farmers and the scale of breeding have increased. ③ Correct, ④ Wrong; When the price of pork rises, residents' food expenditure will increase, the proportion of food expenditure in total household expenditure will increase, the Engel coefficient of residents in this area will increase, and the living standard of residents will decrease. ① Wrong, ② Right. Choose b for this topic.