How Is MTBF Related to FR(N)

Multiple Choice

How is MTBF related to FR(N) ?

A) MTBF is measured in hours, while FR(N) is measured in years.
B) MTBF is normally distributed, with FR(%) as its mean and FR(N) as its standard deviation.
C) MTBF is the reciprocal of FR(N) .
D) Both MTBF and FR(N) increase when breakdown maintenance is replaced by preventive maintenance.
E) MTBF and FR(N) are unrelated concepts.