Choose all the fractions that are in simplest form.

4/26

8/21

6/19

9/10

10/22

4/26 can be simplified by 2. So, this is not the answer.

8/21 cannot be simplified. So, it is one of the answers.

6/19 cannot be simplified. So, it is one of the answers.

9/10 cannot be simplified. So, it is one of the answers.

10/22 can be simplified by 2. So, this is not the answer.

So, the fractions in simplest forms are 8/21, 6/19, and 9/10.