句子改写:下面的句子分别存在几种常见的写作错误(语法问题、指代不清、垂悬修饰语、赘言),请逐一进行改写。 But it may occur some new problems. 修改后:__________________________ [注:需填写完整的句子] Opportunities are only belonged to those who work hard. 修改后:______________________ My grandmother told my mother she couldn't accept the invitation. 修改后:__________________ They will send the food to the exhibition center that we have ordered. 修改后:________________ To improve one's writing skill, regular practice is essential. 修改后:__________________ As your best friend ever, the wedding is an occasion I couldn't miss. 修改后:__________________ In my opinion, I believe the free medical system is in need of reform. 修改后:_________________ People try to find a solution to solve the problem. 修改后:_____________________