The correct answer is: "because it can hire workers quickly if the price rises"
The elasticity of supply measures the percentage change in the quantity supplied cause by a certain price variation. According to the law of supply, price and quantity supply are directly related hence, when price increases so does the quantity supplied.
When there is a % increase in the price of the product, if the quantity supplied increases in a larger proportion, then the supply curve is elastic. Meanwhile, if the % change in the quantity supplied is smaller than the price variation then the supply curve is inelastic.
The supply side in the dog-walking business is constituted by the number of dog-walkers that are willing to do this job at the different prices paid for this service. If this supply is elastic, it means that when the price increases, there is a quick increase in the number of people available for the job.