Explanation:
A movement along the demand curve for soft drinks is best described as a change in quantity demanded. This refers to a change in the quantity of a good that consumers are willing and able to buy in response to a change in price, while all other factors remain constant.

Factors that can cause a movement along the demand curve include:

1. Change in price: An increase in the price of soft drinks will result in a decrease in the quantity demanded, while a decrease in price will result in an increase in the quantity demanded.

2. Change in consumer income: If consumer income increases, they are likely to buy more soft drinks, resulting in an increase in quantity demanded. Conversely, if consumer income decreases, they are likely to buy fewer soft drinks, resulting in a decrease in quantity demanded.

3. Change in tastes and preferences: If soft drinks become more popular, consumers will be willing to buy more of them, resulting in an increase in quantity demanded. If soft drinks become less popular, consumers will be willing to buy fewer of them, resulting in a decrease in quantity demanded.

4. Change in the price of substitutes: If the price of a substitute for soft drinks (such as water or juice) increases, consumers will be more likely to buy soft drinks, resulting in an increase in quantity demanded. Conversely, if the price of a substitute decreases, consumers will be less likely to buy soft drinks, resulting in a decrease in quantity demanded.

In conclusion, a movement along the demand curve for soft drinks is a change in quantity demanded, which is caused by a change in price or other factors such as consumer income, tastes and preferences, and the price of substitutes.