be difficult to sb还是 be difficult for sb.? 到底该用哪个介词啊?

是be difficult to sb 还是be difficult for sb? be difficult to sb还是 be difficult for sb.? 到底该用哪个介词啊? be useful to sb还是for sb? be embarrassing to sb还是for sb? be important to sb还是for sb be rude to sb还是for sb be important to sb.还是be important for sb.区别? be free to sb 还是 be free for sb ..快速.. be free to sb还是be free for sb 是be free to sb 还是be free for sb be familiar to sb还是sth be kind to do sth还是be kind to sb? The problem was too difficult to be solved还是The problem was too difficult to solve? 英文语法：be sorry toor sb?是be sorry to sb还是be sorry for sb? be kind to sb还是be kind of sb还是两者都有,意思不同? 是sb be the admitted to还是sb be admitted to?我又记错笔记了? 是be up to sb to do还是doing? 和某人结婚用英语怎么说?是be married to sb.还是be married with sb.?