Which of the following is valid assignment?

A. > x <- fact(c("yes", "yes", "no", "yes", "no"))

B. > x <- factor(c("yes", "yes", "no", "yes", "no"))

C. > x <- factor(factor("yes", "yes", "no", "yes", "no"))

D. > x <- factor(factor("yes", "no", "no", "yes", "no"))

Answer: Option B