The correct answer is a. context effect.

This is because the given case explains an increase in the demand level with a reduction in the price level. This effect can be explained as the context effect of price level on the level of demand. Meanwhile, the risk-aversion effect is majorly considered in the investment and insurance market. Self-control effect cannot be considered in this case as the demand is price elastic. The extent of variation in demand is determined by the price variation of wines.