sad的比较级和最高级怎么写

例句：

1、How sad that all his hard work should come to nothing.

他的'所有辛勤劳动竟全部付诸东流，太让人伤心了。

2、It's a sad fact that many of those killed were children.

让人难以接受的是遇难者中很多是孩子。

3、It was sad to see them go.

看着他们离去，真让人难过。