Answer:
air
Step-by-step explanation:
San Francisco is located on the SouthWest corner of the United States, while other states such as New York, Boston, adn Philadelphia are located on the NorthEast corner of the United States. This means that the ships are not an option since they would have to go all the way around and would be the longest option. Therefore, the best and fastest option would be through air. Since both railroads and trucks are viable but would take much longer than sending the flowers through air.