The supply and demand curves reflect data for a specific brand of sunglasses. Which circumstance can explains the shift of the demand curve from d to d1?

The question is incomplete. A shift of curve from d to d1 shows a decrease in quantity demanded

Explanation:

the reasons could include

1) the availability of substitutes, if there is a better product that is introduced than the sunglasses in question then the demand for sunglasses are likely to decrease

2) the changes in consumers' income, if the incomes decrease the quantity demanded is likely to decrease causing a shift in demand.

3) if demand for complimentary goods for sunglasses the demand for sunglasses decreases.