What should you check after opening a bottle of wine before serving?

After opening a bottle of wine, checking the appearance for haziness is important because it can indicate the wine's condition. A hazy or cloudy appearance may suggest that the wine has faults, such as contamination, or that it has not been properly stored or handled. This could impact its taste and overall quality, making it necessary to assess before serving.

While the other choices have their own merits, they are less critical in the context of assessing the wine’s quality right after opening. For instance, examining the smell of the cork can be indicative of some issues, particularly with corked wines, but it is not as directly related to the wine itself as checking for haziness. Similarly, while ensuring the bottle is cold may be important for certain types of wines, it does not impact the wine's integrity once opened. Lastly, the price tag being attached is more relevant to the retail context rather than a quality assessment of the wine itself.