💡 Detailed Explanation
The correct choice is Option 3: 'Wash the vegetables.' The cooking teacher explicitly states the steps: 'まず、野菜を洗いましょう' (First, let's wash the vegetables). Following that, they should peel them ('皮をむいて') and chop them ('小さく切ってください'). The meat will be cut later ('肉は後で切ります'). Thus, washing the vegetables is the very first step.