Which of the Following Is an Example of Frictional Unemployment

Which of the following is an example of frictional unemployment?

A) Dora lost her job when the textile factory closed. She does not have skills to work in another industry and has been unemployed for over a year.
B) Marsha was laid off from her job with the airline because the recession has reduced the demand for airline travel. She expects to get her job back when the economy picks up.
C) George is an unskilled worker who mows lawns in the summer, but is unemployed the rest of the year.
D) Hector looked for a job for five weeks after finishing college. He turned down several jobs that didn't fit his skills, but now has a job that requires the expertise he gained in college.