1. I seldom trust the workers in that company, most of whom talk much but do very little. 这里可以把whom改成them吗？

2. You might try your lck in Beijing, where there are a lot of job opportunities. 这里where 可以换成because或者 in which吗？

还有一个不是定语从句的问题麻烦老师也解答一下

3. He failed to win the race, but the courage shown by him made him into a hero. 这里为什么用shown呢，was shown不可以吗？