_ is a method of procurement where a contract results from a bid which may be changed through bargaining.

Thanks for invitation....I endorse answers given by colleagues &Experts

Option -  E Contract Negotiation

It is E - Contract negotiation ( or procurement negotiation ) .

Option -  E Contract Negotiation

(Option B is only meant to confuse people. The KEY DIFFERENCE between contract negotiaion and purchase negotiation is that it can not change the T&C's of contract like penalities, discretions/ non-doscretions, penalties, SLAs for service/ product performance. It can only negotiate around pricing & payments logistics or minor variation in delivery schedule (within the permissible limits of project slack) - e.g. Contract list that vendor will receive payment of X% on certain milestone or will receive payment against Goods receipt. Now purchase negotiaion can happen around1. Credit Period of payment2. Mode of Payment - via direct bank transfer or via LC  (Letter of Credit) release3. Logistics for service delivery etc.

Agree with Mr Md. Fazlur Rahman.

The correct answer is 

E. Contract negotiation

E. Contract negotiation......................................

if the contract is already gone for bids and signed then after all it is not possible to change any item of the contract or to  bargain it for other bidders may protest ,only non official minor changes can happen by mutual understanding and at the personal relation level

E. Contract negotiation...

is my option,...thanks

thanks for invition ,,,,,,,,,, my choice is option E

Thanks, E is the suitable answer.