Which of these are simple sentences and which are fragments?

1) Bats are the true acrobats of the sky.

2) Biobots are changing.

3) I could not answer.

4) Sloths are amazing animals.

5) So we face big and difficult challenges.

6) We do not quit.

7) Wintriness responded to wintriness.

8) Human nature takes its shape in the years between one and five.

9) Education can sometimes seem overwhelming

10) People who have seen them running wild in Russia.

Surprisingly, out of this list of ten things, eight of them are sentences, and only two are fragments.

1) Bats are the true acrobats of the sky. - - simple sentence

2) Biobots are changing. - - simple sentence

3) I could not answer. - - simple sentence

4) Sloths are amazing animals. - - simple sentence

5) So we face big and difficult challenges. - - fragment

6) We do not quit. - - simple sentence

7) Wintriness responded to wintriness. - - simple sentence

8) Human nature takes its shape in the years between one and five. - - sentence

9) Education can sometimes seem overwhelming - - simple sentence

10) People who have seen them running wild in Russia. - - fragment