Which of the following can be used to prevent suppliers form outbidding the lead bid by marginal amounts? Note: there are 2 correct answers to this question.

Which of the following can be used to prevent suppliers form outbidding the lead bid by marginal amounts? Note: there are 2 correct answers to this question.
A . Bid decrement
B. Protect lead bid with front buffer of
C. Protect lead bid with back buffer of
D. Bid guardian percentage

Answer: A,D