As Apple Inc. gears up for the critical holiday season, the tech giant faces uncertainty in one of its most important markets — China. While Apple’s latest quarterly earnings revealed overall revenue growth, challenges in China, where revenue fell to $15 billion, remain a concern. The company projects sales growth of only low- to mid-single digits this holiday season, lower than the 7% that analysts had forecast. The company’s struggles are amplified by its dependence on the Chinese market, both as a major manufacturing hub and a significant consumer base. Competition from domestic brands and …