Past participle: dug. They dug a deep hole in the hillside.

It is inevitable to set a set of wrong questions when learning English. You can correct and analyze the wrong questions in the exam in each assignment and sort them into a group of wrong questions. You can take it out regularly to review and consolidate it, which will greatly improve cloze, composition correction and written expression. Before the exam, you can also focus on reviewing the knowledge points in the wrong book, or even just review the key and difficult points marked in the wrong book, which often leads to unexpected results.