SAN FRANCISCO (AP) — Google, a company built on finding quick answers to people's questions, suddenly finds itself grappling for a response to a potential threat to its internet empire — a form of artificial intelligence that long-time rival Microsoft is now deploying to attack its dominant search engine. Microsoft's assault combined with concerns about Google's ability to ward it off hammered its corporate parent, Alphabet Inc., whose stock price plunged nearly 8% Wednesday in a selloff that wiped out about $100 billion in shareholder wealth. It marked the steepest one-day decline since October when an Alphabet earnings report disclosed a slowdown in digital ad revenue that rattled investors.