Why____he worked very hard at his lessons,only to fail in th

Why____he worked very hard at his lessons,only to fail in th Every student works very hard at his or her lessons He will fail if he doesn't work hard at his lessons同义 he studied hard ONLY to fail in the exam 意思? Bob was clever,but he never worked hard at his lessons.“I mu 英语翻译Harry always worked hard.He did well in his lessons when He has been worked hard ___his lessons.用at还是in啊? Jack worked very hard at every Tom works very hard at his lessons.He did not get the first so,my elder brother,worked very hard at his study,and,my you 英语句子：Mary studied hard only to fail in the exam. She worked very hard in class_______.