Problem with IEnumerator?

Question

C++ / C#

Guys, there is such a timer. It seems to work, but if in Ienumerator-e which is responsible for the correctness of the answer, remove "yield return new WaitForSeconds(1f);" - the timer goes astray and goes twice as fast. If you do not remove it, then after the correct answer there is a long wait for a new question. Where is the mistake?