Surfing—the art of riding a wave on a pointed board—is the wildest, fastest natural water sport known to man. In recent years, it has developed into a major sport around the world, from Australia
________ that I was puzzled. A．So difficult a question did he ask me B．Such difficult a question did he ask me C．Such a difficult question he asked me D．He asked me a so difficult question
+5×4×3×1×
=420种涂色方式.