翻译：我发现这些问题很容易解决.
1.主句为I find...,后面是一个省略引导词that的宾语从句：these problems are easy _____.
2.该句型是英语中常见的不定式主动结构表示被动含义的句型：sb/sth + be + 形容词 + to do,该句型可以转化理解为：It be + 形容词 + to do + sb/sth.
其中：该句型的主语sb/sth,同时也是不定式中的逻辑宾语.
3.如：English is easy to learn.英语很容易学.
= It is easy to learn English.
再如：The man is hard to work with.这个男人很难与之共事.
= It is hard to work with the man.
4.所以此题答案为C,即：these problems are easy to work out.= it is easy to work out these problems.这些问题很容易（被）解决.
因为these problems同时又是work out的宾语,所以BD中的them多余重复；
而A项使用了不定式的被动结构,不符合该句型的特征,排除.