Final answer:
In German superstition, it is considered bad luck to toast with water, as it's akin to toasting with the dead in the underworld, according to Greek mythology.
Step-by-step explanation:
In German superstition, it is considered bad luck to toast with water. This belief stems from Greek mythology where the dead would toast with water in the underworld. It is thought that toasting with water could be wishing death upon yourself or suggesting that you are toasting with those who are no longer alive. Therefore, the answer is A) Water. While toasting with other beverages like wine, beer, or milk does not carry the same superstitious weight in German culture, making a toast with water is traditionally frowned upon.