Answer:
Any movement which is caused by price will be along the demand curve and any other movement caused by non price factors will shift the demand curve.
1) A decrease in the number of consumers is a non price movement so the demand curve will shift leftwards because of it.
2) A change in taste of consumers making them desire more hot dogs is a non price movement and it will shift the demand curve to the right.
3) An increase in the price of hot dogs is a price movement and this will cause movement along the demand curve.
Explanation: