Final answer:
The expression representing the price of 2 gallons of milk is 2x, which is option A. This is calculated by multiplying the price per gallon, represented by x, by 2.
Step-by-step explanation:
To find the expression that represents the price of 2 gallons of milk, we need to know the price per gallon of milk. If we use 'x' to represent the price per gallon, then the price of 2 gallons of milk would be '2 times x', because we have 2 gallons and each one costs 'x' dollars.
The correct expression is therefore 2x, which corresponds to option A. This represents the total price when you buy 2 gallons of milk at 'x' dollars per gallon.