① The demand curve of eggs is inclined downward, so the price drops, and the corresponding demand increases, so the demand increases

② The demand of eggs and pigs is substitutive, so the demand of pigs decreases, the demand curve moves to the left, and the equilibrium of intersection with the supply curve moves to the left and the price drops.

③ The relationship between grain (i.e. feed) and pigs is complementary, and the increase of grain price leads to the decrease of grain demand (the principle is the same as ①). The reason for the decrease of grain demand is that pigs eat less, why? Because the supply of pigs is less = = the supply curve moves to the left.

typing is so tiring ~