Which of the following is true of the methods and tools used to evaluate contractor proposals?

a. after a contract is signed, organizations can negotiate with bidders on cost reductions for specific line items.

b. contractors who have not yet been used can be evaluated using contractor rating systems

c. in a weighing system, each objective criterion is assigned a weight that reflects how expert reviewers feel the contractor satisfies the criterion

d. exception review investigates bid line items that are too high or low in comparison to other bids received