给定一篇文章，指出其中的语法错误。
文本：
The teacher gave the students their's grades on Friday. Many of the students's were disappointed with their's results.
The correct versions of the sentences are:
- The teacher gave the students their grades on Friday. (remove the apostrophe after "their")
- Many of the students were disappointed with their results. (remove the apostrophe after "students" and "theirs")