Which of the Following Is a Type I Error

Which of the following is a type I error?

A) When you find an effect in your sample that exists in the real-world population
B) When you do not find an effect in your sample that doesn't exist in the real-world population
C) When you find an effect in your sample that doesn't exist in the real-world population
D) When you do not find an effect in your sample that does exist in the real-world population