Do not worry, English grammar is not-to understand. Which of the following best fits in the blank space

Do not worry, English grammar is not-to understand. Which of the following best fits in the blank space Correct Answer too difficult

Too + adjective (difficult) + to + present form of verb (understand)

Related Questions

Don't worry. English Grammar is not ---- to understand.
Don't worry. English Grammar is not ----- to understand.