Do we ever make mistakes? Have you ever made this mistake?

We sometimes make mistakes because of inattention.

If the subject doesn´t agree with the verb, you will make
 the same mistake time after time.
Even English speakers make mistakes once in a while.

Not everybody is proud of their own mistakes.

Only the most alert-minded students are able
to check their mistakes before handing the tests in.

Some students were so hard-working that they repeated
all the exercises before the term exams
so that they could avoid making those mistakes again.

"Luckily you all will have corrected some grammar errors,
which are silly and easy to solve,
 by the end of the semester", the old professor stated.

Some explanations are so incredibly complicated
that teachers have to post their lessons
so that the students can concentrate on the topic completely.