Al and his father decided to make mayonnaise. Al wasn't sure he'd like anything that didn't come from a jar, but his father said Al was in for a big treat, so off they went. They gathered the ingredients they'd need: oil, egg yolks, a special mustard, and pepper and salt. Al turned on the blender and watched as his father liquefied the yolks. Then Al watched him drizzle the oil very slowly into the yolks. The mixture began to turn white and slowly thicken. Al's father flicked in some salt and pepper and the mustard and, presto, it was finished. Al took a taste and smiled. "It does taste better than mayonnaise in the jar," he said. Question Which ingredient did Al's father put in the blender first?