According to the law of demand, assuming other factors are held constant

a. as the price of milk decreases, the quantity of milk demanded will increase.
b. as the demand for milk increases, the price of milk will also increase.
c. as the price of milk increases, the quantity of milk demanded will increase.

a. As the price of milk decreases, the quantity of milk demanded will increase.

Explanation:

According to the law of demand, if the price of a commodity is increasing than the quantity demanded of a commodity is decreased, and if the price of a commodity is decrease than the quantity demanded of a commodity is increased.  

It means that it shows an inverse relationship between the price and the quantity demanded of a commodity.

In this, only two factors are changed, and the other factors are being constant

ans.

heterothermic organisms include those organisms that can switch between homeothermic (having body temperature higher than environment) and poikilothermic (having variation in internal body temperature) strategies.

some migratory birds show heterothermy as they decrease their metabolic rate during cold nights to keep their body temperature low. drop in metabolic rate allows increase in production efficiency of birds that reduces the internal body temperature to make it equal to external cold temperature during cold nights.

thus, the correct answer is 'birds allow their temperature drop in order to increase their production efficiency.'

i would say iii (3) because in order to compare a price you have to use as a reference other near stores because it's its

hope i explained myself