Question: What year was the California theme park, which features the steel Kong roller coaster, opened?
Sentence (from "Six Flags Discovery Kingdom"): Six Flags Discovery Kingdom (formerly known as Six Flags Marine World, Marine World, The New Marine World Theme Park, and Marine World Africa USA) is a 135-acre (55 ha) animal theme park located in Vallejo, California, roughly halfway between San Francisco and Sacramento on Interstate 80.
Relevant evidence: No