Which is correct and most complete?

a. Random variables are unknown by the planner at time of planning.

b. Applying any quality technology is generally associated with some risk that can be estimated using probability theory and/or judgment.

c. Even though method evaluation involves subjectivity, the same methods can be compared thoroughly using the same assumptions.

d. All of the above are correct.

e. All of the above are correct except

(a) and (d).